What to use when writing conditions after where in sql

The conditions after the WHERE clause are used to filter the returned data. The conditions usually use operators such as equal to, not equal to, greater than, less than, etc. LIKE, IN, BETWEEN, etc. can also be used. Conditions can be combined using logical operators AND, OR, NOT. For example, WHERE salary > 50000 AND department = 'Sales' filters for employees with a salary greater than $50,000 and a department of "Sales".

Conditions following the WHERE clause in SQL

In SQL queries, the WHERE clause is used to specify Certain conditions to filter the returned data. These conditions can be applied to any column in the table.

The condition that follows the WHERE clause usually uses one of the following operators:

• Equals ( = ): Checks whether two values ​​are equal.
• Not equal to (<>): Checks whether two values ​​are not equal.
• Greater than ( > ): Check whether the left value is greater than the right value.
• Less than ( < ): Checks whether the left value is less than the right value.
• Greater than or equal to ( >= ): Checks whether the left value is greater than or equal to the right value.
• Less than or equal to (<=): Checks whether the left value is less than or equal to the right value.
• LIKE: is used to match text patterns.
• IN: Used to check whether a value belongs to a set of values.
• BETWEEN: Used to check whether a value is between two values.

Example:

The following query selects all customers whose names begin with "John" from the table named "customers":

SELECT * FROM customers WHERE name LIKE 'John%';

The following query selects all orders with a total order total greater than $100 from the table named "orders":

SELECT * FROM orders WHERE total > 100;

In the WHERE clause, the syntax of the condition is usually:

列名 运算符 值

Condition Can be combined using logical operators such as AND, OR, and NOT. For example, the following query selects all employees with a salary greater than $50,000 and the department "Sales" from a table named "employees":

SELECT * FROM employees WHERE salary > 50000 AND department = 'Sales';

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