What are the conditional judgment statements in sql

Conditional judgment statements in SQL are used to determine whether conditions are true or false and perform corresponding operations. There are two main types: IF-ELSE statement: different statements are executed depending on whether the condition is true or false. CASE statement: Returns different results based on conditional matching.

Conditional judgment statements in SQL

Conditional judgment statements are used in SQL to determine whether a specific condition is true or false, and perform different actions accordingly. There are two main types of conditional judgment statements:

1. IF-ELSE statement

<code class="sql">IF (condition) THEN statement1
ELSE statement2</code>

• condition: Condition to be evaluated .
• statement1: Statement to be executed if the condition is true.
• statement2: Statement to be executed if the condition is false.

2. CASE statement

<code class="sql">CASE
  WHEN condition1 THEN result1
  WHEN condition2 THEN result2
  ...
  ELSE default_result
END</code>

• condition1, condition2, ...: Condition to be evaluated.
• result1, result2, ...: The result returned if the corresponding condition is true.
• default_result: The default result returned if all conditions are false (optional).

Example

• IF-ELSE statement

<code class="sql">IF (age > 18) THEN
  PRINT "成年"
ELSE
  PRINT "未成年"</code>

• CASE statement

<code class="sql">CASE
  WHEN gender = 'M' THEN "男性"
  WHEN gender = 'F' THEN "女性"
  ELSE "其他"
END</code>

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