带有 IF/THEN/ELSE 的 MySQL 存储过程答案

【问题标题】：MySQL Stored Procedure with IF/THEN/ELSE带有 IF/THEN/ELSE 的 MySQL 存储过程
【发布时间】：2011-10-08 18:36:41
【问题描述】：

我有一个 MySQL 存储过程，其中包含以下 WHILE 语句。

我已经确认@RowCnt 是1，@MaxRows 是6090，但是经过进一步调试，我意识到WHILE 语句正在经历一次迭代并且没有继续；所以我希望对可能导致这种情况的原因有所了解。

完全披露：我将它从 SQL Server 移植到 MySQL 存储过程，这是我以前从未做过的。（意思是 SQL Server，移植 OR 存储过程..）

WHILE @RowCnt <= @MaxRows DO
    SELECT @currentReadSeq:=ReadSeq, @currentReadStrength:=ReadStrength, @currentReadDateTime:=ReadDateTime, @currentReaderID:=ReaderID FROM tblTempRead WHERE rownum = @RowCnt;

    IF ( ((@lastReadSeq + 10) > @currentReadSeq) AND (@lastReaderId = @currentReaderId) ) THEN 
        SET @lastReadSeq = @currentReadSeq, @lastReadStrength = @currentReadStrength, @lastReadDateTime = @currentReadDateTime, @lastReaderID = @currentReaderID;
    ELSE
        INSERT INTO tblreaddataresults (SiteID, ReadDateTimeStart, ReadDateTimeEnd, ReadSeqStart, ReadSeqEnd, ReaderID, DirectSeconds) VALUES ('1002', @saveReadDateTime, @lastReadDateTime, @saveReadSeq, @lastReadSeq, @lastReaderID, timestampdiff(SECOND,@saveReadDateTime,@lastReadDateTime));

        SET @saveReadSeq = @currentReadSeq, @saveReadStrength = @currentReadStrength, @saveReadDateTime = @currentReadDateTime, @saveReaderID = @currentReaderID;

        SET @lastReadSeq = @saveReadSeq, @lastReadStrength = @saveReadStrength, @lastReadDateTime = @saveReadDateTime, @lastReaderID = @saveReaderID;
    END IF;

    SET @RowCnt = @RowCnt+1;
END WHILE;

【问题讨论】：

尝试设置continue handler 以查看您的查询是否有错误，如果触发了错误，您就知道出了什么问题。 dev.mysql.com/doc/refman/5.0/en/declare-handler.html您可以通过插入虚拟表来调试 SP 调用。
WHILE 运行一次，并在 IF 语句正下方点击 SET。运行一次就退出了。

标签： mysql sql-server stored-procedures

【解决方案1】：

试试这个构造

WHILE (@RowCnt <= @MaxRows)
BEGIN
    SELECT @currentReadSeq:=ReadSeq, @currentReadStrength:=ReadStrength, @currentReadDateTime:=ReadDateTime, @currentReaderID:=ReaderID FROM tblTempRead WHERE rownum = @RowCnt;

    IF (((@lastReadSeq + 10) > @currentReadSeq) AND (@lastReaderId = @currentReaderId))
        BEGIN
        SET @lastReadSeq = @currentReadSeq, @lastReadStrength = @currentReadStrength, @lastReadDateTime = @currentReadDateTime, @lastReaderID = @currentReaderID;
        END
    ELSE
        BEGIN
        INSERT INTO tblreaddataresults (SiteID, ReadDateTimeStart, ReadDateTimeEnd,ReadSeqStart, ReadSeqEnd, ReaderID, DirectSeconds) VALUES ('1002',@saveReadDateTime, @lastReadDateTime, @saveReadSeq, @lastReadSeq, @lastReaderID,timestampdiff(SECOND,@saveReadDateTime,@lastReadDateTime));
        SET @saveReadSeq = @currentReadSeq, @saveReadStrength = @currentReadStrength, @saveReadDateTime = @currentReadDateTime, @saveReaderID = @currentReaderID;
        SET @lastReadSeq = @saveReadSeq, @lastReadStrength = @saveReadStrength,@lastReadDateTime = @saveReadDateTime, @lastReaderID = @saveReaderID;
        END
    SET @RowCnt = @RowCnt+1;
END

【讨论】：