{"id":8055,"date":"2019-08-30T02:06:10","date_gmt":"2019-08-30T09:06:10","guid":{"rendered":"http:\/\/www.mysqltutorial.org\/?page_id=8055"},"modified":"2020-07-12T00:44:24","modified_gmt":"2020-07-12T07:44:24","slug":"mysql-check-constraint-emulation","status":"publish","type":"page","link":"https:\/\/www.mysqltutorial.org\/mysql-basics\/mysql-check-constraint-emulation\/","title":{"rendered":"MySQL CHECK Constraint Emulation"},"content":{"rendered":"\n<p><strong>Summary<\/strong>: in this tutorial, you will learn how to use emulate <code>CHECK<\/code> constraints in MySQL using triggers or views.<\/p>\n\n\n\n<p class=\"note\">MySQL 8.0.16 fully implemented the SQL <code>CHECK<\/code> constraint. If you use MySQL 8.0.16 or later, check it out the <a href=\"https:\/\/www.mysqltutorial.org\/mysql-basics\/mysql-check-constraint\/\"><code>CHECK<\/code> constraint<\/a> tutorial.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Emulating CHECK constraints using triggers<\/h2>\n\n\n\n<p>To emulate <code>CHECK<\/code> constraints in MySQL, you can use two <a href=\"https:\/\/www.mysqltutorial.org\/mysql-triggers\/\">triggers<\/a>: <code>BEFORE INSERT<\/code> and <code>BEFORE UPDATE<\/code>.<\/p>\n\n\n\n<p>First, <a href=\"https:\/\/www.mysqltutorial.org\/mysql-basics\/mysql-create-table\/\">create a new table<\/a> named&nbsp;&nbsp;<code>parts<\/code>&nbsp;for the demonstration:<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-1\" data-shcb-language-name=\"SQL (Structured Query Language)\" data-shcb-language-slug=\"sql\"><span><code class=\"hljs language-sql\"><span class=\"hljs-keyword\">CREATE<\/span> <span class=\"hljs-keyword\">TABLE<\/span> <span class=\"hljs-keyword\">IF<\/span> <span class=\"hljs-keyword\">NOT<\/span> <span class=\"hljs-keyword\">EXISTS<\/span> parts (\n    part_no <span class=\"hljs-built_in\">VARCHAR<\/span>(<span class=\"hljs-number\">18<\/span>) PRIMARY <span class=\"hljs-keyword\">KEY<\/span>,\n    description <span class=\"hljs-built_in\">VARCHAR<\/span>(<span class=\"hljs-number\">40<\/span>),\n    <span class=\"hljs-keyword\">cost<\/span> <span class=\"hljs-built_in\">DECIMAL<\/span>(<span class=\"hljs-number\">10<\/span> , <span class=\"hljs-number\">2<\/span> ) <span class=\"hljs-keyword\">NOT<\/span> <span class=\"hljs-literal\">NULL<\/span>,\n    price <span class=\"hljs-built_in\">DECIMAL<\/span>(<span class=\"hljs-number\">10<\/span>,<span class=\"hljs-number\">2<\/span>) <span class=\"hljs-keyword\">NOT<\/span> <span class=\"hljs-literal\">NULL<\/span>\n);<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-1\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">SQL (Structured Query Language)<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">sql<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n\n<p>Next, create a <a href=\"https:\/\/www.mysqltutorial.org\/mysql-stored-procedure\/\">stored procedure<\/a> to check the values in the <code>cost<\/code> and <code>price<\/code> columns.<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-2\" data-shcb-language-name=\"SQL (Structured Query Language)\" data-shcb-language-slug=\"sql\"><span><code class=\"hljs language-sql\">DELIMITER $\n\n<span class=\"hljs-keyword\">CREATE<\/span> <span class=\"hljs-keyword\">PROCEDURE<\/span> <span class=\"hljs-string\">`check_parts`<\/span>(<span class=\"hljs-keyword\">IN<\/span> <span class=\"hljs-keyword\">cost<\/span> <span class=\"hljs-built_in\">DECIMAL<\/span>(<span class=\"hljs-number\">10<\/span>,<span class=\"hljs-number\">2<\/span>), <span class=\"hljs-keyword\">IN<\/span> price <span class=\"hljs-built_in\">DECIMAL<\/span>(<span class=\"hljs-number\">10<\/span>,<span class=\"hljs-number\">2<\/span>))\n<span class=\"hljs-keyword\">BEGIN<\/span>\n    <span class=\"hljs-keyword\">IF<\/span> <span class=\"hljs-keyword\">cost<\/span> &lt; <span class=\"hljs-number\">0<\/span> <span class=\"hljs-keyword\">THEN<\/span>\n        SIGNAL <span class=\"hljs-keyword\">SQLSTATE<\/span> <span class=\"hljs-string\">'45000'<\/span>\n           <span class=\"hljs-keyword\">SET<\/span> MESSAGE_TEXT = <span class=\"hljs-string\">'check constraint on parts.cost failed'<\/span>;\n    <span class=\"hljs-keyword\">END<\/span> <span class=\"hljs-keyword\">IF<\/span>;\n    \n    IF price &lt; 0 THEN\n\tSIGNAL SQLSTATE '45001'\n\t   <span class=\"hljs-keyword\">SET<\/span> MESSAGE_TEXT = <span class=\"hljs-string\">'check constraint on parts.price failed'<\/span>;\n    <span class=\"hljs-keyword\">END<\/span> <span class=\"hljs-keyword\">IF<\/span>;\n    \n    IF price &lt; cost THEN\n\tSIGNAL SQLSTATE '45002'\n           <span class=\"hljs-keyword\">SET<\/span> MESSAGE_TEXT = <span class=\"hljs-string\">'check constraint on parts.price &amp; parts.cost failed'<\/span>;\n    <span class=\"hljs-keyword\">END<\/span> <span class=\"hljs-keyword\">IF<\/span>;\n<span class=\"hljs-keyword\">END<\/span>$\nDELIMITER ;<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-2\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">SQL (Structured Query Language)<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">sql<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n\n<p>Then, create&nbsp;<code>BEFORE INSERT<\/code>&nbsp;and <code>BEFORE UPDATE<\/code> triggers. Inside the triggers, call the <code>check_parts()<\/code> stored procedure.<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-3\" data-shcb-language-name=\"SQL (Structured Query Language)\" data-shcb-language-slug=\"sql\"><span><code class=\"hljs language-sql\"><span class=\"hljs-comment\">-- before insert<\/span>\nDELIMITER $\n<span class=\"hljs-keyword\">CREATE<\/span> <span class=\"hljs-keyword\">TRIGGER<\/span> <span class=\"hljs-string\">`parts_before_insert`<\/span> <span class=\"hljs-keyword\">BEFORE<\/span> <span class=\"hljs-keyword\">INSERT<\/span> <span class=\"hljs-keyword\">ON<\/span> <span class=\"hljs-string\">`parts`<\/span>\n<span class=\"hljs-keyword\">FOR<\/span> <span class=\"hljs-keyword\">EACH<\/span> <span class=\"hljs-keyword\">ROW<\/span>\n<span class=\"hljs-keyword\">BEGIN<\/span>\n    <span class=\"hljs-keyword\">CALL<\/span> check_parts(new.cost,new.price);\n<span class=\"hljs-keyword\">END<\/span>$   \nDELIMITER ; \n<span class=\"hljs-comment\">-- before update<\/span>\nDELIMITER $\n<span class=\"hljs-keyword\">CREATE<\/span> <span class=\"hljs-keyword\">TRIGGER<\/span> <span class=\"hljs-string\">`parts_before_update`<\/span> <span class=\"hljs-keyword\">BEFORE<\/span> <span class=\"hljs-keyword\">UPDATE<\/span> <span class=\"hljs-keyword\">ON<\/span> <span class=\"hljs-string\">`parts`<\/span>\n<span class=\"hljs-keyword\">FOR<\/span> <span class=\"hljs-keyword\">EACH<\/span> <span class=\"hljs-keyword\">ROW<\/span>\n<span class=\"hljs-keyword\">BEGIN<\/span>\n    <span class=\"hljs-keyword\">CALL<\/span> check_parts(new.cost,new.price);\n<span class=\"hljs-keyword\">END<\/span>$   \nDELIMITER ;<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-3\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">SQL (Structured Query Language)<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">sql<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n\n<p>After that, <a href=\"https:\/\/www.mysqltutorial.org\/mysql-basics\/mysql-insert\/\">insert<\/a> a new row that satisfies all the following conditions:<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>cost &gt; 0<\/li><li>And price &gt; 0<\/li><li>And price &nbsp;&gt;= cost<\/li><\/ul>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-4\" data-shcb-language-name=\"SQL (Structured Query Language)\" data-shcb-language-slug=\"sql\"><span><code class=\"hljs language-sql\"><span class=\"hljs-keyword\">INSERT<\/span> <span class=\"hljs-keyword\">INTO<\/span> parts(part_no, description,<span class=\"hljs-keyword\">cost<\/span>,price)\n<span class=\"hljs-keyword\">VALUES<\/span>(<span class=\"hljs-string\">'A-001'<\/span>,<span class=\"hljs-string\">'Cooler'<\/span>,<span class=\"hljs-number\">100<\/span>,<span class=\"hljs-number\">120<\/span>);<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-4\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">SQL (Structured Query Language)<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">sql<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n<pre class=\"wp-block-code\"><span><code class=\"hljs\">1 row(s) affected<\/code><\/span><\/pre>\n\n\n<p>The <code>INSERT<\/code> statement invokes the <code>BEFORE INSERT<\/code> trigger and accepts the values.<\/p>\n\n\n\n<p>The following <code>INSERT<\/code> statement&nbsp;fails because it violates the&nbsp;condition: cost &gt; 0.<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-5\" data-shcb-language-name=\"SQL (Structured Query Language)\" data-shcb-language-slug=\"sql\"><span><code class=\"hljs language-sql\"><span class=\"hljs-keyword\">INSERT<\/span> <span class=\"hljs-keyword\">INTO<\/span> parts(part_no, description,<span class=\"hljs-keyword\">cost<\/span>,price)\n<span class=\"hljs-keyword\">VALUES<\/span>(<span class=\"hljs-string\">'A-002'<\/span>,<span class=\"hljs-string\">'Heater'<\/span>,<span class=\"hljs-number\">-100<\/span>,<span class=\"hljs-number\">120<\/span>);<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-5\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">SQL (Structured Query Language)<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">sql<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-6\" data-shcb-language-name=\"SQL (Structured Query Language)\" data-shcb-language-slug=\"sql\"><span><code class=\"hljs language-sql\">Error Code: 1644. <span class=\"hljs-keyword\">check<\/span> <span class=\"hljs-keyword\">constraint<\/span> <span class=\"hljs-keyword\">on<\/span> parts.cost <span class=\"hljs-keyword\">failed<\/span><\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-6\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">SQL (Structured Query Language)<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">sql<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n\n<p>The following <code>INSERT<\/code> statement fails because it violates the condition: price &gt; 0.<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-7\" data-shcb-language-name=\"SQL (Structured Query Language)\" data-shcb-language-slug=\"sql\"><span><code class=\"hljs language-sql\"><span class=\"hljs-keyword\">INSERT<\/span> <span class=\"hljs-keyword\">INTO<\/span> parts(part_no, description,<span class=\"hljs-keyword\">cost<\/span>,price)\n<span class=\"hljs-keyword\">VALUES<\/span>(<span class=\"hljs-string\">'A-002'<\/span>,<span class=\"hljs-string\">'Heater'<\/span>,<span class=\"hljs-number\">100<\/span>,<span class=\"hljs-number\">-120<\/span>);<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-7\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">SQL (Structured Query Language)<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">sql<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-8\" data-shcb-language-name=\"JavaScript\" data-shcb-language-slug=\"javascript\"><span><code class=\"hljs language-javascript\"><span class=\"hljs-built_in\">Error<\/span> Code: <span class=\"hljs-number\">1644.<\/span> check constraint on parts.price failed<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-8\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">JavaScript<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">javascript<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n\n<p>The following <code>INSERT<\/code> statement fails because it violates the condition: price &gt; cost.<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-9\" data-shcb-language-name=\"SQL (Structured Query Language)\" data-shcb-language-slug=\"sql\"><span><code class=\"hljs language-sql\"><span class=\"hljs-keyword\">INSERT<\/span> <span class=\"hljs-keyword\">INTO<\/span> parts(part_no, description,<span class=\"hljs-keyword\">cost<\/span>,price)\n<span class=\"hljs-keyword\">VALUES<\/span>(<span class=\"hljs-string\">'A-003'<\/span>,<span class=\"hljs-string\">'wiper'<\/span>,<span class=\"hljs-number\">120<\/span>,<span class=\"hljs-number\">100<\/span>);<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-9\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">SQL (Structured Query Language)<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">sql<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n\n<p>Let&#8217;s see what we are having now in&nbsp;the <code>parts<\/code> table.<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-10\" data-shcb-language-name=\"SQL (Structured Query Language)\" data-shcb-language-slug=\"sql\"><span><code class=\"hljs language-sql\"><span class=\"hljs-keyword\">SELECT<\/span> * <span class=\"hljs-keyword\">FROM<\/span> parts;<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-10\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">SQL (Structured Query Language)<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">sql<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n\n<figure class=\"wp-block-image\"><img loading=\"lazy\" decoding=\"async\" width=\"252\" height=\"44\" src=\"https:\/\/www.mysqltutorial.org\/wp-content\/uploads\/2016\/05\/MySQL-CHECK-Constraint-Emulation-Example.png\" alt=\"MySQL CHECK Constraint Emulation Example\" class=\"wp-image-5285\"\/><\/figure>\n\n\n\n<p>The following statement attempt to update the cost to make it lower than the price:<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-11\" data-shcb-language-name=\"SQL (Structured Query Language)\" data-shcb-language-slug=\"sql\"><span><code class=\"hljs language-sql\"><span class=\"hljs-keyword\">UPDATE<\/span> parts\n<span class=\"hljs-keyword\">SET<\/span> price = <span class=\"hljs-number\">10<\/span>\n<span class=\"hljs-keyword\">WHERE<\/span> part_no = <span class=\"hljs-string\">'A-001'<\/span>;<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-11\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">SQL (Structured Query Language)<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">sql<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-12\" data-shcb-language-name=\"SQL (Structured Query Language)\" data-shcb-language-slug=\"sql\"><span><code class=\"hljs language-sql\">Error Code: 1644. <span class=\"hljs-keyword\">check<\/span> <span class=\"hljs-keyword\">constraint<\/span> <span class=\"hljs-keyword\">on<\/span> parts.price &amp; parts.cost <span class=\"hljs-keyword\">failed<\/span><\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-12\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">SQL (Structured Query Language)<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">sql<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n\n<p>The statement was rejected.<\/p>\n\n\n\n<p>So by using two triggers: <code>BEFORE INSERT<\/code> and <code>BEFORE UPDATE<\/code>, you are able to emulate <code>CHECK<\/code> constraints in MySQL.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Emulate CHECK constraints using views<\/h2>\n\n\n\n<p>The idea is to create a view <code>WITH CHECK OPTION<\/code> based on the underlying table. In the <code><a href=\"https:\/\/www.mysqltutorial.org\/mysql-basics\/mysql-select-from\/\">SELECT<\/a><\/code> statement of the view definition, we select only valid rows that satisfy the <code>CHECK<\/code> conditions. Any insert or update against the view will be rejected if it causes the new row to not appear in the view.<\/p>\n\n\n\n<p>First, drop the <code>parts<\/code> table to remove all the associated triggers and <a href=\"https:\/\/www.mysqltutorial.org\/mysql-basics\/mysql-create-table\/\">create a new table<\/a> like the <code>parts<\/code> table but have a different name <code>parts_data<\/code>:<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-13\" data-shcb-language-name=\"SQL (Structured Query Language)\" data-shcb-language-slug=\"sql\"><span><code class=\"hljs language-sql\"><span class=\"hljs-keyword\">DROP<\/span> <span class=\"hljs-keyword\">TABLE<\/span> <span class=\"hljs-keyword\">IF<\/span> <span class=\"hljs-keyword\">EXISTS<\/span> parts;\n\n<span class=\"hljs-keyword\">CREATE<\/span> <span class=\"hljs-keyword\">TABLE<\/span> <span class=\"hljs-keyword\">IF<\/span> <span class=\"hljs-keyword\">NOT<\/span> <span class=\"hljs-keyword\">EXISTS<\/span> parts_data (\n    part_no <span class=\"hljs-built_in\">VARCHAR<\/span>(<span class=\"hljs-number\">18<\/span>) PRIMARY <span class=\"hljs-keyword\">KEY<\/span>,\n    description <span class=\"hljs-built_in\">VARCHAR<\/span>(<span class=\"hljs-number\">40<\/span>),\n    <span class=\"hljs-keyword\">cost<\/span> <span class=\"hljs-built_in\">DECIMAL<\/span>(<span class=\"hljs-number\">10<\/span>,<span class=\"hljs-number\">2<\/span>) <span class=\"hljs-keyword\">NOT<\/span> <span class=\"hljs-literal\">NULL<\/span>,\n    price <span class=\"hljs-built_in\">DECIMAL<\/span>(<span class=\"hljs-number\">10<\/span>,<span class=\"hljs-number\">2<\/span>) <span class=\"hljs-keyword\">NOT<\/span> <span class=\"hljs-literal\">NULL<\/span>\n);\n<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-13\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">SQL (Structured Query Language)<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">sql<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n\n<p>Next, <a href=\"https:\/\/www.mysqltutorial.org\/mysql-views\/mysql-create-view\/\">create a view<\/a> named <code>parts<\/code> based on the <code>parts_data<\/code> table. By doing this, we can&nbsp;keep the code of the applications that use the <code>parts<\/code> table remains intact. In addition, all the privileges to the old <code>parts<\/code> table remains unchanged.<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-14\" data-shcb-language-name=\"SQL (Structured Query Language)\" data-shcb-language-slug=\"sql\"><span><code class=\"hljs language-sql\"><span class=\"hljs-keyword\">CREATE<\/span> <span class=\"hljs-keyword\">VIEW<\/span> parts <span class=\"hljs-keyword\">AS<\/span>\n    <span class=\"hljs-keyword\">SELECT<\/span> \n        part_no, description, <span class=\"hljs-keyword\">cost<\/span>, price\n    <span class=\"hljs-keyword\">FROM<\/span>\n        parts_data\n    <span class=\"hljs-keyword\">WHERE<\/span>\n        <span class=\"hljs-keyword\">cost<\/span> &gt; <span class=\"hljs-number\">0<\/span> <span class=\"hljs-keyword\">AND<\/span> price &gt; <span class=\"hljs-number\">0<\/span> <span class=\"hljs-keyword\">AND<\/span> price &gt;= <span class=\"hljs-keyword\">cost<\/span> \n<span class=\"hljs-keyword\">WITH<\/span> <span class=\"hljs-keyword\">CHECK<\/span> <span class=\"hljs-keyword\">OPTION<\/span>;<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-14\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">SQL (Structured Query Language)<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">sql<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n\n<p>Then, <a href=\"https:\/\/www.mysqltutorial.org\/mysql-basics\/mysql-insert\/\">insert a new row<\/a> into the <code>parts_data<\/code> table through the <code>parts<\/code> view:<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-15\" data-shcb-language-name=\"SQL (Structured Query Language)\" data-shcb-language-slug=\"sql\"><span><code class=\"hljs language-sql\"><span class=\"hljs-keyword\">INSERT<\/span> <span class=\"hljs-keyword\">INTO<\/span> parts(part_no, description,<span class=\"hljs-keyword\">cost<\/span>,price)\n<span class=\"hljs-keyword\">VALUES<\/span>(<span class=\"hljs-string\">'A-001'<\/span>,<span class=\"hljs-string\">'Cooler'<\/span>,<span class=\"hljs-number\">100<\/span>,<span class=\"hljs-number\">120<\/span>);<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-15\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">SQL (Structured Query Language)<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">sql<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n\n<p>It is accepted because the new row is valid which appears in the view.<\/p>\n\n\n\n<p>After that, attempt to insert a new row that would not appear in the view.<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-16\" data-shcb-language-name=\"SQL (Structured Query Language)\" data-shcb-language-slug=\"sql\"><span><code class=\"hljs language-sql\"><span class=\"hljs-keyword\">INSERT<\/span> <span class=\"hljs-keyword\">INTO<\/span> parts_checked(part_no, description,<span class=\"hljs-keyword\">cost<\/span>,price)\n<span class=\"hljs-keyword\">VALUES<\/span>(<span class=\"hljs-string\">'A-002'<\/span>,<span class=\"hljs-string\">'Heater'<\/span>,<span class=\"hljs-number\">-100<\/span>,<span class=\"hljs-number\">120<\/span>);\n<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-16\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">SQL (Structured Query Language)<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">sql<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-17\" data-shcb-language-name=\"JavaScript\" data-shcb-language-slug=\"javascript\"><span><code class=\"hljs language-javascript\"><span class=\"hljs-built_in\">Error<\/span> Code: <span class=\"hljs-number\">1369.<\/span> CHECK OPTION failed <span class=\"hljs-string\">'classicmodels.parts_checked'<\/span><\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-17\"><span class=\"shcb-language__label\">Code language:<\/span> <span class=\"shcb-language__name\">JavaScript<\/span> <span class=\"shcb-language__paren\">(<\/span><span class=\"shcb-language__slug\">javascript<\/span><span class=\"shcb-language__paren\">)<\/span><\/small><\/pre>\n\n\n<p>In this tutorial, you have learned how to use triggers or views to emulate the <code>CHECK<\/code> constraints in MySQL.<\/p>\n<div class=\"helpful-block-content\" data-title=\"\">\n\t<header>\n\t\t<div class=\"wth-question\">Was this tutorial helpful? <\/div>\n\t\t<div class=\"wth-thumbs\">\n\t\t\t<button\n\t\t\t\tdata-post=\"8055\"\n\t\t\t\tdata-post-url=\"https:\/\/www.mysqltutorial.org\/mysql-basics\/mysql-check-constraint-emulation\/\"\n\t\t\t\tdata-post-title=\"MySQL CHECK Constraint Emulation\"\n\t\t\t\tdata-response=\"1\"\n\t\t\t\tclass=\"wth-btn-rounded wth-yes-btn\"\n\t\t\t>\n\t\t\t\t<svg\n\t\t\t\t\txmlns=\"http:\/\/www.w3.org\/2000\/svg\"\n\t\t\t\t\tviewBox=\"0 0 24 24\"\n\t\t\t\t\tfill=\"none\"\n\t\t\t\t\tstroke=\"currentColor\"\n\t\t\t\t\tstroke-width=\"2\"\n\t\t\t\t\tstroke-linecap=\"round\"\n\t\t\t\t\tstroke-linejoin=\"round\"\n\t\t\t\t\tclass=\"feather feather-thumbs-up block w-full h-full\"\n\t\t\t\t>\n\t\t\t\t\t<path\n\t\t\t\t\t\td=\"M14 9V5a3 3 0 0 0-3-3l-4 9v11h11.28a2 2 0 0 0 2-1.7l1.38-9a2 2 0 0 0-2-2.3zM7 22H4a2 2 0 0 1-2-2v-7a2 2 0 0 1 2-2h3\"\n\t\t\t\t\t><\/path>\n\t\t\t\t<\/svg>\n\t\t\t\t<span class=\"sr-only\"> Yes <\/span>\n\t\t\t<\/button>\n\n\t\t\t<button\n\t\t\t\tdata-response=\"0\"\n\t\t\t\tdata-post=\"8055\"\n\t\t\t\tdata-post-url=\"https:\/\/www.mysqltutorial.org\/mysql-basics\/mysql-check-constraint-emulation\/\"\n\t\t\t\tdata-post-title=\"MySQL CHECK Constraint Emulation\"\n\t\t\t\tclass=\"wth-btn-rounded wth-no-btn\"\n\t\t\t>\n\t\t\t\t<svg\n\t\t\t\t\txmlns=\"http:\/\/www.w3.org\/2000\/svg\"\n\t\t\t\t\tviewBox=\"0 0 24 24\"\n\t\t\t\t\tfill=\"none\"\n\t\t\t\t\tstroke=\"currentColor\"\n\t\t\t\t\tstroke-width=\"2\"\n\t\t\t\t\tstroke-linecap=\"round\"\n\t\t\t\t\tstroke-linejoin=\"round\"\n\t\t\t\t>\n\t\t\t\t\t<path\n\t\t\t\t\t\td=\"M10 15v4a3 3 0 0 0 3 3l4-9V2H5.72a2 2 0 0 0-2 1.7l-1.38 9a2 2 0 0 0 2 2.3zm7-13h2.67A2.31 2.31 0 0 1 22 4v7a2.31 2.31 0 0 1-2.33 2H17\"\n\t\t\t\t\t><\/path>\n\t\t\t\t<\/svg>\n\t\t\t\t<span class=\"sr-only\"> No <\/span>\n\t\t\t<\/button>\n\t\t<\/div>\n\t<\/header>\n\n\t<div class=\"wth-form hidden\">\n\t\t<div class=\"wth-form-wrapper\">\n\t\t\t<div class=\"wth-title\"><\/div>\n\t\t\t\n\t\t\t<textarea class=\"wth-message\"><\/textarea>\n\n\t\t\t<button class=\"btn btn-primary wth-btn-submit\">Send<\/button>\n\t\t\t<button class=\"btn wth-btn-cancel\">Cancel<\/button>\n\t\t\n\t\t<\/div>\n\t<\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"<p>In this tutorial, you will learn how to use triggers or views to emulate the CHECK constraints in MySQL.<\/p>\n","protected":false},"author":2,"featured_media":0,"parent":174,"menu_order":106,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-8055","page","type-page","status-publish","hentry"],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v27.5 - https:\/\/yoast.com\/product\/yoast-seo-wordpress\/ -->\n<title>MySQL CHECK Constraint Emulation<\/title>\n<meta name=\"description\" content=\"In this tutorial, you will learn how to use triggers or views to emulate the CHECK constraints in MySQL.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.mysqltutorial.org\/mysql-check-constraint-emulation\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"MySQL CHECK Constraint Emulation\" \/>\n<meta property=\"og:description\" content=\"In this tutorial, you will learn how to use triggers or views to emulate the CHECK constraints in MySQL.\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.mysqltutorial.org\/mysql-check-constraint-emulation\/\" \/>\n<meta property=\"og:site_name\" content=\"MySQL Tutorial\" \/>\n<meta property=\"article:modified_time\" content=\"2020-07-12T07:44:24+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/www.mysqltutorial.org\/wp-content\/uploads\/2016\/05\/MySQL-CHECK-Constraint-Emulation-Example.png\" \/>\n<meta name=\"twitter:label1\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data1\" content=\"4 minutes\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\\\/\\\/schema.org\",\"@graph\":[{\"@type\":\"WebPage\",\"@id\":\"https:\\\/\\\/www.mysqltutorial.org\\\/mysql-check-constraint-emulation\\\/\",\"url\":\"https:\\\/\\\/www.mysqltutorial.org\\\/mysql-check-constraint-emulation\\\/\",\"name\":\"MySQL CHECK Constraint Emulation\",\"isPartOf\":{\"@id\":\"https:\\\/\\\/www.mysqltutorial.org\\\/#website\"},\"primaryImageOfPage\":{\"@id\":\"https:\\\/\\\/www.mysqltutorial.org\\\/mysql-check-constraint-emulation\\\/#primaryimage\"},\"image\":{\"@id\":\"https:\\\/\\\/www.mysqltutorial.org\\\/mysql-check-constraint-emulation\\\/#primaryimage\"},\"thumbnailUrl\":\"https:\\\/\\\/www.mysqltutorial.org\\\/wp-content\\\/uploads\\\/2016\\\/05\\\/MySQL-CHECK-Constraint-Emulation-Example.png\",\"datePublished\":\"2019-08-30T09:06:10+00:00\",\"dateModified\":\"2020-07-12T07:44:24+00:00\",\"description\":\"In this tutorial, you will learn how to use triggers or views to emulate the CHECK constraints in MySQL.\",\"breadcrumb\":{\"@id\":\"https:\\\/\\\/www.mysqltutorial.org\\\/mysql-check-constraint-emulation\\\/#breadcrumb\"},\"inLanguage\":\"en-US\",\"potentialAction\":[{\"@type\":\"ReadAction\",\"target\":[\"https:\\\/\\\/www.mysqltutorial.org\\\/mysql-check-constraint-emulation\\\/\"]}]},{\"@type\":\"ImageObject\",\"inLanguage\":\"en-US\",\"@id\":\"https:\\\/\\\/www.mysqltutorial.org\\\/mysql-check-constraint-emulation\\\/#primaryimage\",\"url\":\"https:\\\/\\\/www.mysqltutorial.org\\\/wp-content\\\/uploads\\\/2016\\\/05\\\/MySQL-CHECK-Constraint-Emulation-Example.png\",\"contentUrl\":\"https:\\\/\\\/www.mysqltutorial.org\\\/wp-content\\\/uploads\\\/2016\\\/05\\\/MySQL-CHECK-Constraint-Emulation-Example.png\",\"width\":252,\"height\":44},{\"@type\":\"BreadcrumbList\",\"@id\":\"https:\\\/\\\/www.mysqltutorial.org\\\/mysql-check-constraint-emulation\\\/#breadcrumb\",\"itemListElement\":[{\"@type\":\"ListItem\",\"position\":1,\"name\":\"Home\",\"item\":\"https:\\\/\\\/www.mysqltutorial.org\\\/\"},{\"@type\":\"ListItem\",\"position\":2,\"name\":\"MySQL Basics\",\"item\":\"https:\\\/\\\/www.mysqltutorial.org\\\/mysql-basics\\\/\"},{\"@type\":\"ListItem\",\"position\":3,\"name\":\"MySQL CHECK Constraint Emulation\"}]},{\"@type\":\"WebSite\",\"@id\":\"https:\\\/\\\/www.mysqltutorial.org\\\/#website\",\"url\":\"https:\\\/\\\/www.mysqltutorial.org\\\/\",\"name\":\"MySQL Tutorial\",\"description\":\"A comprehensive MySQL Tutorial\",\"potentialAction\":[{\"@type\":\"SearchAction\",\"target\":{\"@type\":\"EntryPoint\",\"urlTemplate\":\"https:\\\/\\\/www.mysqltutorial.org\\\/?s={search_term_string}\"},\"query-input\":{\"@type\":\"PropertyValueSpecification\",\"valueRequired\":true,\"valueName\":\"search_term_string\"}}],\"inLanguage\":\"en-US\"}]}<\/script>\n<!-- \/ Yoast SEO plugin. -->","yoast_head_json":{"title":"MySQL CHECK Constraint Emulation","description":"In this tutorial, you will learn how to use triggers or views to emulate the CHECK constraints in MySQL.","robots":{"index":"index","follow":"follow","max-snippet":"max-snippet:-1","max-image-preview":"max-image-preview:large","max-video-preview":"max-video-preview:-1"},"canonical":"https:\/\/www.mysqltutorial.org\/mysql-check-constraint-emulation\/","og_locale":"en_US","og_type":"article","og_title":"MySQL CHECK Constraint Emulation","og_description":"In this tutorial, you will learn how to use triggers or views to emulate the CHECK constraints in MySQL.","og_url":"https:\/\/www.mysqltutorial.org\/mysql-check-constraint-emulation\/","og_site_name":"MySQL Tutorial","article_modified_time":"2020-07-12T07:44:24+00:00","og_image":[{"url":"https:\/\/www.mysqltutorial.org\/wp-content\/uploads\/2016\/05\/MySQL-CHECK-Constraint-Emulation-Example.png","type":"","width":"","height":""}],"twitter_misc":{"Est. reading time":"4 minutes"},"schema":{"@context":"https:\/\/schema.org","@graph":[{"@type":"WebPage","@id":"https:\/\/www.mysqltutorial.org\/mysql-check-constraint-emulation\/","url":"https:\/\/www.mysqltutorial.org\/mysql-check-constraint-emulation\/","name":"MySQL CHECK Constraint Emulation","isPartOf":{"@id":"https:\/\/www.mysqltutorial.org\/#website"},"primaryImageOfPage":{"@id":"https:\/\/www.mysqltutorial.org\/mysql-check-constraint-emulation\/#primaryimage"},"image":{"@id":"https:\/\/www.mysqltutorial.org\/mysql-check-constraint-emulation\/#primaryimage"},"thumbnailUrl":"https:\/\/www.mysqltutorial.org\/wp-content\/uploads\/2016\/05\/MySQL-CHECK-Constraint-Emulation-Example.png","datePublished":"2019-08-30T09:06:10+00:00","dateModified":"2020-07-12T07:44:24+00:00","description":"In this tutorial, you will learn how to use triggers or views to emulate the CHECK constraints in MySQL.","breadcrumb":{"@id":"https:\/\/www.mysqltutorial.org\/mysql-check-constraint-emulation\/#breadcrumb"},"inLanguage":"en-US","potentialAction":[{"@type":"ReadAction","target":["https:\/\/www.mysqltutorial.org\/mysql-check-constraint-emulation\/"]}]},{"@type":"ImageObject","inLanguage":"en-US","@id":"https:\/\/www.mysqltutorial.org\/mysql-check-constraint-emulation\/#primaryimage","url":"https:\/\/www.mysqltutorial.org\/wp-content\/uploads\/2016\/05\/MySQL-CHECK-Constraint-Emulation-Example.png","contentUrl":"https:\/\/www.mysqltutorial.org\/wp-content\/uploads\/2016\/05\/MySQL-CHECK-Constraint-Emulation-Example.png","width":252,"height":44},{"@type":"BreadcrumbList","@id":"https:\/\/www.mysqltutorial.org\/mysql-check-constraint-emulation\/#breadcrumb","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https:\/\/www.mysqltutorial.org\/"},{"@type":"ListItem","position":2,"name":"MySQL Basics","item":"https:\/\/www.mysqltutorial.org\/mysql-basics\/"},{"@type":"ListItem","position":3,"name":"MySQL CHECK Constraint Emulation"}]},{"@type":"WebSite","@id":"https:\/\/www.mysqltutorial.org\/#website","url":"https:\/\/www.mysqltutorial.org\/","name":"MySQL Tutorial","description":"A comprehensive MySQL Tutorial","potentialAction":[{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https:\/\/www.mysqltutorial.org\/?s={search_term_string}"},"query-input":{"@type":"PropertyValueSpecification","valueRequired":true,"valueName":"search_term_string"}}],"inLanguage":"en-US"}]}},"_links":{"self":[{"href":"https:\/\/www.mysqltutorial.org\/wp-json\/wp\/v2\/pages\/8055","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.mysqltutorial.org\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/www.mysqltutorial.org\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/www.mysqltutorial.org\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.mysqltutorial.org\/wp-json\/wp\/v2\/comments?post=8055"}],"version-history":[{"count":0,"href":"https:\/\/www.mysqltutorial.org\/wp-json\/wp\/v2\/pages\/8055\/revisions"}],"up":[{"embeddable":true,"href":"https:\/\/www.mysqltutorial.org\/wp-json\/wp\/v2\/pages\/174"}],"wp:attachment":[{"href":"https:\/\/www.mysqltutorial.org\/wp-json\/wp\/v2\/media?parent=8055"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}