case when usage in plsql

CASE WHEN in PL/SQL is a conditional statement that performs different actions based on conditions. Syntax: CASE WHEN condition THEN result ELSE default result END; Advantages: more concise, easy to read, and can be nested. Limitation: Only single value conditions can be processed, the result must be a single value.

CASE WHEN usage in PL/SQL

What is CASE WHEN?

CASE WHEN is a conditional statement in PL/SQL that is used to perform different actions based on specified conditions.

Syntax

<code>CASE
  WHEN 条件1 THEN 结果1
  WHEN 条件2 THEN 结果2
  ...
  ELSE 默认结果
END;</code>

Usage

1. Define conditions: WHEN clause specifies the Check the conditions.
2. Specify the result: THEN clause specifies the result to be returned if the condition is true.
3. Set the default value: The ELSE clause specifies the result to be returned if all conditions are not met.

Example

<code>-- 将数字转换为月份名称
CASE score
  WHEN 1 THEN 'January'
  WHEN 2 THEN 'February'
  WHEN 3 THEN 'March'
  ELSE 'Unknown'
END;</code>

Advantages

• Can be used as an alternative to the IF-ELSEIF-ELSE statement A more concise and readable approach.
• Multiple CASE WHEN statements can be nested to handle more complex conditions.

Limitations

• Can only handle single value conditions and cannot be used to handle ranges or lists.
• The result of the CASE WHEN statement must be a single value, not a table or cursor.

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