{"id":90,"date":"2016-03-22T13:00:13","date_gmt":"2016-03-22T13:00:13","guid":{"rendered":"https:\/\/sqltutorial.org\/?page_id=90"},"modified":"2025-02-04T07:20:23","modified_gmt":"2025-02-04T14:20:23","slug":"sql-where","status":"publish","type":"page","link":"https:\/\/www.sqltutorial.org\/sql-where\/","title":{"rendered":"SQL WHERE"},"content":{"rendered":"\r\n

Summary<\/strong>: in this tutorial, you will learn how to use the SQL WHERE<\/code> clause to filter rows based on one or more conditions.<\/p>\r\n\r\n\r\n\r\n

Introduction to SQL WHERE clause #<\/a><\/h2>\r\n\r\n\r\n\r\n

To select specific rows from a table based on one or more conditions, you use the WHERE<\/code> clause in the SELECT<\/a><\/code> statement.<\/p>\r\n\r\n\r\n\r\n

Here’s the syntax of the WHERE<\/code> clause:<\/p>\r\n\r\n\r\n

SELECT<\/span> \r\n    column1, column2, ...\r\nFROM<\/span>\r\n    table_name\r\nWHERE<\/span>\r\n    condition;<\/code><\/span>Code language:<\/span> SQL (Structured Query Language)<\/span> (<\/span>sql<\/span>)<\/span><\/small><\/pre>\r\n\r\n\r\n
The WHERE<\/code> clause appears immediately after the FROM<\/code> clause.\u00a0It contains one or more Boolean expressions that evaluate each row in the table.<\/p>\r\n\r\n\r\n\r\n
If a row that causes the condition evaluates to true<\/code>, the query will include that row in the result set.<\/p>\r\n\r\n\r\n\r\n
Note that SQL has three-valued logic which are true<\/code>, false<\/code>, and NULL<\/code>. It means that if a row causes the condition<\/code> to evaluate to false<\/code> or null<\/code>, the query will not include that row in the result set.<\/p>\r\n\r\n\r\n\r\n
The condition that follows the WHERE<\/code> clause is also known as a predicate. You can use operators to form a flexible condition to filter rows.<\/p>\r\n\r\n\r\n\r\n
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Operator<\/th>\r\nMeaning<\/th>\r\n<\/tr>\r\n<\/thead>\r\n
=<\/td>\r\nEqual to<\/td>\r\n<\/tr>\r\n
<> (!=)<\/td>\r\nNot equal to<\/td>\r\n<\/tr>\r\n
<<\/td>\r\nLess than<\/td>\r\n<\/tr>\r\n
><\/td>\r\nGreater than<\/td>\r\n<\/tr>\r\n
<=<\/td>\r\nLess than or equal<\/td>\r\n<\/tr>\r\n
>=<\/td>\r\nGreater than or equal<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n<\/figure>\r\n\r\n\r\n\r\n
To construct a simple condition, you use one of the operators above with two operands that can be column name on one side and a literal value on the other, for example:<\/p>\r\n\r\n\r\n
salary > 1000<\/code><\/span>Code language:<\/span> SQL (Structured Query Language)<\/span> (<\/span>sql<\/span>)<\/span><\/small><\/pre>\r\n\r\n\r\n
It asks the question: “Is salary greater than 1000?”.<\/p>\r\n\r\n\r\n\r\n
Or you can use column names on both sides of an operator such as:<\/p>\r\n\r\n\r\n
min_salary < max_salary<\/code><\/span>Code language:<\/span> SQL (Structured Query Language)<\/span> (<\/span>sql<\/span>)<\/span><\/small><\/pre>\r\n\r\n\r\n
This expression asks another question: “Is the minimum salary less than the maximum salary?”.<\/p>\r\n\r\n\r\n\r\n
The literal values you use in a condition can be numbers, strings, dates, and times. Here are typical formats:<\/p>\r\n\r\n\r\n\r\n
The following table shows the SQL comparison operators<\/a>:<\/p>\r\n\r\n\r\n\r\n