Usage of loop in sql

LOOP is a control structure in T-SQL that is used to repeatedly execute statement blocks until specific conditions are met. It provides loop control, flexibility, and simplicity, but also requires attention to exit conditions and potential infinite loops.

LOOP usage in SQL

What is LOOP

LOOP Is a control structure in Transact-SQL (T-SQL) that allows a set of statements to be executed repeatedly until a specific condition is met.

Syntax

<code>LOOP
  -- 语句块
  EXIT WHEN <condition>;
END LOOP</code>

Usage

LOOP works as follows:

1. Execute statement piece.
2. Check EXIT WHEN condition.
3. If the condition is true, exit the LOOP.
4. If the condition is false, repeat steps 1 and 2.

Example

The following example uses LOOP to calculate the sum from 1 to 10:

<code>DECLARE @sum INT;
SET @sum = 0;

LOOP
  SET @sum = @sum + 1;
  EXIT WHEN @sum > 10;
END LOOP;

PRINT @sum;</code>

Advantages

LOOP provides the following advantages:

• Loop control: Allows fine control over loop execution.
• Flexibility: Supports custom exit conditions.
• Conciseness: The syntax is more concise than the WHILE loop.

Points to note

You need to pay attention to the following points when using LOOP:

• Exit conditions:EXIT WHEN The condition must be a boolean expression and must ultimately be true to exit the loop.
• Infinite loop: If there is no EXIT WHEN condition, the loop will execute infinitely.
• Alternatives: In some cases, a WHILE loop may be a better alternative to a LOOP.

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