What does if mean in sql

The IF keyword in SQL is used to perform different actions based on conditions. The syntax is: IF condition THEN code_block_1 [ELSE code_block_2]. IF statements can check whether a value is empty, compare values ​​for equality, and perform different operations based on conditions.

The meaning of IF in SQL

IF in SQL is a keyword used to specify when a specific condition The code block to be executed when satisfied. It is a control flow statement that allows performing different actions based on conditions in a SQL query.

Grammar

##IF The syntax of the statement is as follows:

<code>IF condition
THEN code_block_1
[ELSE code_block_2]</code>

Among them:

• condition is the condition to be evaluated.
• code_block_1 is the code block to be executed if condition is true.
• code_block_2 (optional) is the code block to execute if condition is false.

Usage

IF statement can be used in various situations, for example:

Check the value Whether it is empty or not empty
• Compare two values ​​for equality
• Perform different operations based on conditions

Example

The following is a sample query using the

IF statement:

<code>SELECT CASE
    WHEN age >= 18
    THEN '成年人'
    ELSE '未成年人'
END
FROM person;</code>

This query gets the age column from table

person and classifies it as "Adult" based on the conditions person" or "minor".

Note

• #IF There must be a THEN clause in the statement, even if there is no ELSE clause.
• IF statements can be nested within other IF statements. The
• IF statement is often used in conjunction with other control flow statements such as CASE.

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