How do you use the IF statement in SQL?

The IF statement in SQL is used to perform operations conditionally based on specified conditions.

In SQL, the IF statement is a control flow structure that allows you to execute different code blocks based on certain conditions. It is similar to the IF statement in other programming languages. The syntax for the IF statement in SQL is as follows:

```
IF condition THEN
statement_list
[ELSEIF condition THEN
statement_list] ...
[ELSE
statement_list]
END IF;
```

In this syntax, the condition is a Boolean expression that evaluates to TRUE or FALSE. If the condition is TRUE, the statement_list after the THEN keyword is executed. If the condition is FALSE and the ELSEIF clause exists, the condition in the ELSEIF clause is evaluated. If the ELSEIF condition is TRUE, the statement_list after the THEN keyword in the ELSEIF clause is executed. If all conditions are FALSE and the ELSE clause exists, the statement_list in the ELSE clause is executed.

Here is an example of how to use the IF statement in SQL:

```
IF @score >= 60 THEN
SET @grade = 'Pass';
ELSE
SET @grade = 'Fail';
END IF;
```

In this example, if the @score variable is greater than or equal to 60, the @grade variable is set to 'Pass'. Otherwise, the @grade variable is set to 'Fail'.

It's important to note that the IF statement is not supported in all SQL databases. For example, MySQL and SQL Server support the IF statement, but Oracle does not. In Oracle, you would use the IF statement in PL/SQL, which is Oracle's procedural extension of SQL.

In conclusion, the IF statement in SQL is a powerful tool that allows you to control the flow of your SQL scripts. By understanding how to use the IF statement, you can write more flexible and dynamic SQL scripts.