MySQL :: MySQL 8.4 参考手册 :: 15.6.2 声明标签

MySQL 8.4 参考手册 · 中文镜像

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MySQL 8.4 参考手册 / 15 条 SQL 语句 / 15.6 复合语句语法 / 15.6.2 声明标签

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15.6.2 语句标签15.6.2 Statement Labels

[begin_label:] BEGIN
    [statement_list]
END [end_label]

[begin_label:] LOOP
    statement_list
END LOOP [end_label]

[begin_label:] REPEAT
    statement_list
UNTIL search_condition
END REPEAT [end_label]

[begin_label:] WHILE search_condition DO
    statement_list
END WHILE [end_label]

使用标签 BEGIN ... END 块，以及对于 LOOP， REPEAT， WHILE 语句。这些语句的标签使用遵循以下规则：Labels are permitted for BEGIN ... END blocks and for the LOOP, REPEAT, and WHILE statements. Label use for those statements follows these rules:

begin_label must be followed by a colon.
begin_label can be given without end_label。如果end_label is present, it must be the same as begin_label.begin_label can be given without end_label. If end_label is present, it must be the same as begin_label.
end_label cannot be given without begin_label.
同一嵌套层级的标签必须是不同的。Labels at the same nesting level must be distinct.
标签长度可达 16 个字符。Labels can be up to 16 characters long.

在标记结构中引用标签时，可以使用 ITERATE 或 LEAVE 语句。以下示例使用这些语句来继续迭代或终止循环：To refer to a label within the labeled construct, use an ITERATE or LEAVE statement. The following example uses those statements to continue iterating or terminate the loop:

CREATE PROCEDURE doiterate(p1 INT)
BEGIN
  label1: LOOP
    SET p1 = p1 + 1;
    IF p1 < 10 THEN ITERATE label1; END IF;
    LEAVE label1;
  END LOOP label1;
END;

块标签的作用域不包含块内声明的处理器代码。详情请参见第 15.6.7.2 节，“DECLARE ...HANDLER 语句“。The scope of a block label does not include the code for handlers declared within the block. For details, see Section 15.6.7.2, “DECLARE ... HANDLER Statement”.

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