{"id":1166,"date":"2018-01-14T20:57:22","date_gmt":"2018-01-15T03:57:22","guid":{"rendered":"https:\/\/sqltutorial.org\/?page_id=1166"},"modified":"2025-02-08T04:57:27","modified_gmt":"2025-02-08T11:57:27","slug":"sql-subquery","status":"publish","type":"page","link":"https:\/\/www.sqltutorial.org\/sql-subquery\/","title":{"rendered":"SQL Subquery"},"content":{"rendered":"\n<p><strong>Summary<\/strong>: In this tutorial, you&#8217;ll learn how to use SQL subqueries to form flexible queries for retrieving data from the database.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id='introduction-to-sql-subquery'>Introduction to SQL subquery <a href=\"#introduction-to-sql-subquery\" class=\"anchor\" id=\"introduction-to-sql-subquery\" title=\"Anchor for Introduction to SQL subquery\">#<\/a><\/h2>\n\n\n\n<p>A subquery is an SQL query nested inside another <a href=\"https:\/\/www.sqltutorial.org\/sql-select\/\">query<\/a>. The query that contains a subquery is known as an outer query.<\/p>\n\n\n\n<p>To write a subquery, you need to have a deep understanding of the <code>SELECT<\/code> statement:<\/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\">SELECT<\/span>\n  select_list\n<span class=\"hljs-keyword\">FROM<\/span>\n  table1\n  <span class=\"hljs-keyword\">INNER<\/span> <span class=\"hljs-keyword\">JOIN<\/span> table2 <span class=\"hljs-keyword\">ON<\/span> join_condition\n<span class=\"hljs-keyword\">WHERE<\/span>\n  filter_condition;<\/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 class=\"note\">Note that the join can be <code><a href=\"https:\/\/www.sqltutorial.org\/sql-inner-join\/\">INNER JOIN<\/a><\/code>, <code><a href=\"https:\/\/www.sqltutorial.org\/sql-left-join\/\">LEFT JOIN<\/a><\/code>, <code><a href=\"https:\/\/www.sqltutorial.org\/sql-right-join\/\">RIGHT JOIN<\/a><\/code>, or <code><a href=\"https:\/\/www.sqltutorial.org\/sql-full-outer-join\/\">FULL JOIN<\/a><\/code>.<\/p>\n\n\n\n<p>In this syntax:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>The <code>SELECT<\/code> clause can accept a single value, which can be a column or an expression.<\/li>\n\n\n\n<li>The <code>FROM<\/code> and <code>INNER JOIN<\/code> clauses can accept a result set such as a table.<\/li>\n\n\n\n<li>The <code><a href=\"https:\/\/www.sqltutorial.org\/sql-where\/\">WHERE<\/a><\/code> can accept a single value, which can be a column or an expression.<\/li>\n<\/ul>\n\n\n\n<p>Based on the shape of the data each clause accepts, you can embed the appropriate subquery:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>The subquery in the <code>SELECT<\/code> clause can return a single value.<\/li>\n\n\n\n<li>The subquery in the <code>FROM<\/code> or <code>INNER JOIN<\/code> clauses can return a result set.<\/li>\n\n\n\n<li>The subquery in the <code>WHERE<\/code> clause can return a single value.<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\" id='sql-subquery-in-the-where-clause'>SQL subquery in the WHERE clause <a href=\"#sql-subquery-in-the-where-clause\" class=\"anchor\" id=\"sql-subquery-in-the-where-clause\" title=\"Anchor for SQL subquery in the WHERE clause\">#<\/a><\/h2>\n\n\n\n<p>We&#8217;ll use the <code>employees<\/code> table from the <a href=\"https:\/\/www.sqltutorial.org\/sql-sample-database\/\">HR sample database<\/a>:<\/p>\n\n\n\n<figure class=\"wp-block-image size-full\"><img loading=\"lazy\" decoding=\"async\" width=\"169\" height=\"273\" src=\"https:\/\/www.sqltutorial.org\/wp-content\/uploads\/2016\/03\/employees.png\" alt=\"SQL Subquery - employees Table\" class=\"wp-image-237\"\/><\/figure>\n\n\n\n<p>The following statement uses a subquery to find the employees who have the highest salary:<\/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\"><span class=\"hljs-keyword\">SELECT<\/span>\n  first_name,\n  salary\n<span class=\"hljs-keyword\">FROM<\/span>\n  employees\n<span class=\"hljs-keyword\">WHERE<\/span>\n  salary = (\n    <span class=\"hljs-keyword\">SELECT<\/span>\n      <span class=\"hljs-keyword\">MAX<\/span>(salary)\n    <span class=\"hljs-keyword\">FROM<\/span>\n      employees\n  );<\/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><a href=\"https:\/\/www.sqltutorial.org\/playground\/?q=U0VMRUNUIGZpcnN0X25hbWUsIHNhbGFyeSBGUk9NIGVtcGxveWVlcyBXSEVSRSBzYWxhcnkgPSAoIFNFTEVDVCBNQVgoc2FsYXJ5KSBGUk9NIGVtcGxveWVlcyApOw%3D%3D\" target=\"_blank\" rel=\"noreferrer noopener\">Try it<\/a><\/p>\n\n\n\n<p>Output:<\/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\"> first_name |  salary\n<span class=\"hljs-comment\">------------+----------<\/span>\n Steven     | 24000.00<\/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>How the query works.<\/p>\n\n\n\n<p>First, the subquery returns the <a href=\"https:\/\/www.sqltutorial.org\/sql-aggregate-functions\/sql-max\/\">max<\/a> salary from the <code>salary<\/code> column of the <code>employees<\/code> table:<\/p>\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\">SELECT<\/span>\n  <span class=\"hljs-keyword\">MAX<\/span>(salary)\n<span class=\"hljs-keyword\">FROM<\/span>\n  employees<\/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\n<p>Second, the outer query uses the value returned by the subquery and returns the employee with the highest salary.<\/p>\n\n\n\n<p>The following example uses a subquery to find employees with a salary greater than the <a href=\"https:\/\/www.sqltutorial.org\/sql-aggregate-functions\/sql-avg\/\">average<\/a> salary:<\/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\">SELECT<\/span>\n  first_name,\n  salary\n<span class=\"hljs-keyword\">FROM<\/span>\n  employees\n<span class=\"hljs-keyword\">WHERE<\/span>\n  salary &gt; (\n    <span class=\"hljs-keyword\">SELECT<\/span>\n      <span class=\"hljs-keyword\">AVG<\/span>(salary)\n    <span class=\"hljs-keyword\">FROM<\/span>\n      employees\n  )\n<span class=\"hljs-keyword\">ORDER<\/span> <span class=\"hljs-keyword\">BY<\/span>\n  salary;<\/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\n<p><a href=\"https:\/\/www.sqltutorial.org\/playground\/?q=U0VMRUNUIGZpcnN0X25hbWUsIHNhbGFyeSBGUk9NIGVtcGxveWVlcyBXSEVSRSBzYWxhcnkgPiAoIFNFTEVDVCBBVkcoc2FsYXJ5KSBGUk9NIGVtcGxveWVlcyApIE9SREVSIEJZIHNhbGFyeTs%3D\" target=\"_blank\" rel=\"noreferrer noopener\">Try it<\/a><\/p>\n\n\n\n<p>Output:<\/p>\n\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\"> first_name |  salary\n<span class=\"hljs-comment\">------------+----------<\/span>\n John       |  8200.00\n Adam       |  8200.00\n William    |  8300.00\n Jack       |  8400.00\n Jonathon   |  8600.00\n...<\/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<h2 class=\"wp-block-heading\" id='sql-subquery-with-the-in-operator'>SQL Subquery with the IN operator <a href=\"#sql-subquery-with-the-in-operator\" class=\"anchor\" id=\"sql-subquery-with-the-in-operator\" title=\"Anchor for SQL Subquery with the IN operator\">#<\/a><\/h2>\n\n\n\n<p>The <a href=\"https:\/\/www.sqltutorial.org\/sql-in\/\">IN<\/a> operator returns <code>true<\/code> if a value equals any value in a list of values. You can use a subquery to return a list of values for the <code>IN<\/code> operator:<\/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\">IN subquery<\/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\n<p>For example, the following query uses a subquery with the <code>IN<\/code> operator to find all employees with the job titles related to <code>Sales<\/code>:<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-8\" 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>\n  first_name,\n  last_name\n<span class=\"hljs-keyword\">FROM<\/span>\n  employees\n<span class=\"hljs-keyword\">WHERE<\/span>\n  job_id <span class=\"hljs-keyword\">IN<\/span> (\n    <span class=\"hljs-keyword\">SELECT<\/span>\n      job_id\n    <span class=\"hljs-keyword\">FROM<\/span>\n      jobs\n    <span class=\"hljs-keyword\">WHERE<\/span>\n      job_title <span class=\"hljs-keyword\">LIKE<\/span> <span class=\"hljs-string\">'%Sales%'<\/span>\n  );<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-8\"><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><a href=\"https:\/\/www.sqltutorial.org\/playground\/?q=U0VMRUNUIGZpcnN0X25hbWUsIGxhc3RfbmFtZSBGUk9NIGVtcGxveWVlcyBXSEVSRSBqb2JfaWQgSU4gKCBTRUxFQ1Qgam9iX2lkIEZST00gam9icyBXSEVSRSBqb2JfdGl0bGUgTElLRSAnJVNhbGVzJScgKTs%3D\" target=\"_blank\" rel=\"noreferrer noopener\">Try it<\/a><\/p>\n\n\n\n<p>Output:<\/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\"> first_name | last_name\n<span class=\"hljs-comment\">------------+------------<\/span>\n John       | Russell\n Karen      | Partners\n Jonathon   | Taylor\n Jack       | Livingston\n Kimberely  | <span class=\"hljs-keyword\">Grant<\/span>\n Charles    | Johnson<\/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>How the query works.<\/p>\n\n\n\n<p>First, the subquery returns a list of job IDs with the job titles have the word <code>\"Sales\"<\/code>:<\/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>\n  job_id\n<span class=\"hljs-keyword\">FROM<\/span>\n  jobs\n<span class=\"hljs-keyword\">WHERE<\/span>\n  job_title <span class=\"hljs-keyword\">LIKE<\/span> <span class=\"hljs-string\">'%Sales%'<\/span><\/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<p>Output:<\/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\"> job_id\n<span class=\"hljs-comment\">--------<\/span>\n     15\n     16<\/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\n<p>Second, the outer query selects the employees with the <code>job_id<\/code> in the job id list (15, 16).<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id='subquery-in-the-select-clause'>Subquery in the SELECT clause <a href=\"#subquery-in-the-select-clause\" class=\"anchor\" id=\"subquery-in-the-select-clause\" title=\"Anchor for Subquery in the SELECT clause\">#<\/a><\/h2>\n\n\n\n<p>The following example uses a subquery in the <code>SELECT<\/code> clause to retrieve the first name, salary, and average salary of all employees:<\/p>\n\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\"><span class=\"hljs-keyword\">SELECT<\/span>\n  first_name,\n  salary,\n  (\n    <span class=\"hljs-keyword\">SELECT<\/span>\n      <span class=\"hljs-keyword\">ROUND<\/span>(<span class=\"hljs-keyword\">AVG<\/span>(salary),<span class=\"hljs-number\">2<\/span>) average_salary\n    <span class=\"hljs-keyword\">FROM<\/span>\n      employees\n  )\n<span class=\"hljs-keyword\">FROM<\/span>\n  employees\n<span class=\"hljs-keyword\">ORDER<\/span> <span class=\"hljs-keyword\">BY<\/span>\n  salary;<\/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><a href=\"https:\/\/www.sqltutorial.org\/playground\/?q=U0VMRUNUIGZpcnN0X25hbWUsIHNhbGFyeSwgKCBTRUxFQ1QgQVZHKHNhbGFyeSkgRlJPTSBlbXBsb3llZXMgKSBGUk9NIGVtcGxveWVlcyBPUkRFUiBCWSBzYWxhcnk7\" target=\"_blank\" rel=\"noreferrer noopener\">Try it<\/a><\/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\"> first_name  |  salary  | average_salary\n<span class=\"hljs-comment\">-------------+----------+----------------<\/span>\n Karen       |  2500.00 |        8060.00\n Guy         |  2600.00 |        8060.00\n Irene       |  2700.00 |        8060.00\n Sigal       |  2800.00 |        8060.00\n Shelli      |  2900.00 |        8060.00\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<h2 class=\"wp-block-heading\" id='subquery-in-the-from-clause'>Subquery in the FROM clause <a href=\"#subquery-in-the-from-clause\" class=\"anchor\" id=\"subquery-in-the-from-clause\" title=\"Anchor for Subquery in the FROM clause\">#<\/a><\/h2>\n\n\n\n<p>The following example shows how to use a subquery in the <code>FROM<\/code> clause:<\/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\">SELECT<\/span>\n  <span class=\"hljs-keyword\">ROUND<\/span>(<span class=\"hljs-keyword\">AVG<\/span>(department_salary), <span class=\"hljs-number\">0<\/span>) average_department_salary\n<span class=\"hljs-keyword\">FROM<\/span>\n  (\n    <span class=\"hljs-keyword\">SELECT<\/span>\n      department_id,\n      <span class=\"hljs-keyword\">SUM<\/span>(salary) department_salary\n    <span class=\"hljs-keyword\">FROM<\/span>\n      employees\n    <span class=\"hljs-keyword\">GROUP<\/span> <span class=\"hljs-keyword\">BY<\/span>\n      department_id\n  );<\/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><a href=\"https:\/\/www.sqltutorial.org\/playground\/?q=U0VMRUNUIFJPVU5EKEFWRyhkZXBhcnRtZW50X3NhbGFyeSksIDApIGF2ZXJhZ2VfZGVwYXJ0bWVudF9zYWxhcnkgRlJPTSAoIFNFTEVDVCBkZXBhcnRtZW50X2lkLCBhdmcoc2FsYXJ5KSBkZXBhcnRtZW50X3NhbGFyeSBGUk9NIGVtcGxveWVlcyBHUk9VUCBCWSBkZXBhcnRtZW50X2lkICk7\" target=\"_blank\" rel=\"noreferrer noopener\">Try it<\/a><\/p>\n\n\n\n<p>Output:<\/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\"> average_department_salary\n<span class=\"hljs-comment\">---------------------------<\/span>\n                     29309<\/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>How it works.<\/p>\n\n\n\n<p>First, the subquery returns a result set that includes <code>department_id<\/code> and total salary for each department:<\/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\">SELECT<\/span>\n  department_id,\n  <span class=\"hljs-keyword\">SUM<\/span>(salary) department_salary\n<span class=\"hljs-keyword\">FROM<\/span>\n  employees\n<span class=\"hljs-keyword\">GROUP<\/span> <span class=\"hljs-keyword\">BY<\/span>\n  department_id;<\/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\n<p>Second, the outer query calculates the average total salary of all departments and rounds it off with zero decimal places.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\" id='subquery-in-the-inner-join-clause'>Subquery in the INNER JOIN clause <a href=\"#subquery-in-the-inner-join-clause\" class=\"anchor\" id=\"subquery-in-the-inner-join-clause\" title=\"Anchor for Subquery in the INNER JOIN clause\">#<\/a><\/h2>\n\n\n\n<p>The following example uses a subquery in the <code>INNER JOIN<\/code> clause of the outer query to retrieve employees who earn above the company&#8217;s average salary:<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-17\" 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>\n  first_name,\n  last_name,\n  salary,\n  s.avg_salary\n<span class=\"hljs-keyword\">FROM<\/span>\n  employees e\n  <span class=\"hljs-keyword\">INNER<\/span> <span class=\"hljs-keyword\">JOIN<\/span> (\n    <span class=\"hljs-keyword\">SELECT<\/span>\n      <span class=\"hljs-keyword\">ROUND<\/span>(<span class=\"hljs-keyword\">AVG<\/span>(salary), <span class=\"hljs-number\">0<\/span>) <span class=\"hljs-keyword\">AS<\/span> avg_salary\n    <span class=\"hljs-keyword\">FROM<\/span>\n      employees\n  ) s <span class=\"hljs-keyword\">ON<\/span> e.salary &gt; s.avg_salary\n<span class=\"hljs-keyword\">ORDER<\/span> <span class=\"hljs-keyword\">BY<\/span>\n  salary;<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-17\"><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><a href=\"https:\/\/www.sqltutorial.org\/playground\/?q=U0VMRUNUIGZpcnN0X25hbWUsIGxhc3RfbmFtZSwgc2FsYXJ5LCBzLmF2Z19zYWxhcnkgRlJPTSBlbXBsb3llZXMgZSBJTk5FUiBKT0lOICggU0VMRUNUIFJPVU5EKEFWRyhzYWxhcnkpLCAwKSBBUyBhdmdfc2FsYXJ5IEZST00gZW1wbG95ZWVzICkgcyBPTiBlLnNhbGFyeSA%2BIHMuYXZnX3NhbGFyeSBPUkRFUiBCWSBzYWxhcnk7\" target=\"_blank\" rel=\"noreferrer noopener\">Try it<\/a><\/p>\n\n\n\n<p>Output:<\/p>\n\n\n<pre class=\"wp-block-code\" aria-describedby=\"shcb-language-18\" data-shcb-language-name=\"SQL (Structured Query Language)\" data-shcb-language-slug=\"sql\"><span><code class=\"hljs language-sql\"> first_name | last_name  |  salary  | avg_salary\n<span class=\"hljs-comment\">------------+------------+----------+------------<\/span>\n John       | Chen       |  8200.00 |       8060\n Adam       | Fripp      |  8200.00 |       8060\n William    | Gietz      |  8300.00 |       8060\n Jack       | Livingston |  8400.00 |       8060\n Jonathon   | Taylor     |  8600.00 |       8060\n...<\/code><\/span><small class=\"shcb-language\" id=\"shcb-language-18\"><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>How the query works.<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>First, the subquery calculates the company&#8217;s average salary.<\/li>\n\n\n\n<li>Second, the outer query retrieves employees earning above that average salary.<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\" id='summary'>Summary <a href=\"#summary\" class=\"anchor\" id=\"summary\" title=\"Anchor for Summary\">#<\/a><\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li>A subquery is a query nested in an outer query.<\/li>\n\n\n\n<li>Embed an appropriate subquery in the <code>SELECT<\/code>, <code>FROM<\/code>, <code>WHERE<\/code>, and <code>INNER JOIN<\/code> clauses of a query.<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\" id='quiz'>Quiz <a href=\"#quiz\" class=\"anchor\" id=\"quiz\" title=\"Anchor for Quiz\">#<\/a><\/h2>\n\n\n\n<iframe loading=\"lazy\"\n  name=\"quiz\"\n  src=\"\/quiz\/?quiz=subquery\"\n  height=\"700\"\n  width=\"600\"\n  class=\"iframe\"\n><\/iframe>\n\n\n\n\n<h2 class=\"wp-block-heading\" id='databases'>Databases <a href=\"#databases\" class=\"anchor\" id=\"databases\" title=\"Anchor for Databases\">#<\/a><\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li><a href=\"https:\/\/www.pgtutorial.com\/postgresql-tutorial\/postgresql-subquery\/\" target=\"_blank\" rel=\"noreferrer noopener\">PostgreSQL Subquery<\/a><\/li>\n\n\n\n<li><a href=\"https:\/\/www.mysqltutorial.org\/mysql-basics\/mysql-subquery\/\" target=\"_blank\" rel=\"noreferrer noopener\">MySQL Subquery<\/a><\/li>\n\n\n\n<li><a href=\"https:\/\/www.sqlitetutorial.net\/sqlite-subquery\/\" target=\"_blank\" rel=\"noreferrer noopener\">SQLite Subquery<\/a><\/li>\n\n\n\n<li><a href=\"https:\/\/www.db2tutorial.com\/db2-basics\/db2-subquery\/\" target=\"_blank\" rel=\"noreferrer noopener\">Db2 Subquery<\/a><\/li>\n\n\n\n<li><a href=\"https:\/\/www.oracletutorial.com\/oracle-basics\/oracle-subquery\/\" target=\"_blank\" rel=\"noreferrer noopener\">Oracle Subquery<\/a><\/li>\n\n\n\n<li><a href=\"https:\/\/www.sqlservertutorial.net\/sql-server-basics\/sql-server-subquery\/\" target=\"_blank\" rel=\"noreferrer noopener\">SQL Server Subquery<\/a><\/li>\n<\/ul>\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 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