如何在 mysql 的 UDF 中创建两个循环

Posted 2023-04-14

【中文标题】如何在 mysql 的 UDF 中创建两个循环

【英文标题】：How to make TWO loops in a UDF at mysql

【发布时间】：2020-04-18 09:03:08

【问题描述】：

类似于***Posting 我想计算由TITLE1 和TITLE2 组成的m x n 矩阵的Levenshtein 距离。

我的 Levenshtein Functions 工作正常，来自这里：LD 但我的问题是如何在 UDF 中循环遍历 m x n？

结果应该是一个包含m x n 行的表，其中包含 LD、TITLE1 和 TITLE2。

我已经这样做了 - 但我总是出错

     1338 Cursor Declaration after Handler Declaration

我的 UDF 如下所示：

  BEGIN  
       DECLARE bDone INT;
       DECLARE bDone1 INT;

       DECLARE var2 varCHAR(255);    -- or approriate type
       DECLARE Var1 INT;
       DECLARE c1Var1 VARCHAR(250);

       DECLARE curs CURSOR FOR  SELECT recid as BIOTIrecid, replace(replace(BIOGRAPHYTITLE," [in SCOPUS]",""),"[SIMILAR]","") as bioti FROM BIO ;
       DECLARE CONTINUE HANDLER FOR NOT FOUND SET bDone = 1;
       DECLARE curs1 CURSOR FOR  SELECT trim(concat(scopus.Titel," ",scopus.Untertitel)) as scopusti FROM scopus ;
       DECLARE CONTINUE HANDLER FOR NOT FOUND SET bDone = 1;

       DROP  TABLE IF EXISTS LDResults;
        CREATE TABLE `LDResults` (
           `BIOGRAPHYTITLE` varchar(255) DEFAULT NULL,
           `recid` int(11) NOT NULL AUTO_INCREMENT,
           `BIOTIrecid` int(11) default NULL,
           `LD` varchar(255) DEFAULT NULL,
           `ScopusTI` varchar(255) DEFAULT NULL,
           PRIMARY KEY (`recid`)
        ) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;

        OPEN curs1;

        SET bDone1 = 0;
        #---------------- run all rows for scopusti
        REPEAT
            FETCH curs1 into c1var1;

        #-----------------------------------------
            OPEN curs;

            SET bDone = 0;
            #----- run all COLUMNs for biographytitle
            REPEAT
                FETCH curs INTO var1, var2;
                INSERT INTO LDResults (`BIOGRAPHYTITLE`, `BIOTIrecid`, `LD`, `ScopusTI`) VALUES (var2, var1, LEVENSHTEIN(var2,c1var1), c1var1);
            UNTIL bDone END REPEAT;
        #--------------------------------------------
        CLOSE curs;

        UNTIL bDone1 END REPEAT;


       CLOSE curs1;
       SELECT * FROM LDResults;
     END

我解决这个问题的方法是复杂的，还是可以通过更快更好的解决方案来完成？

感谢所有建议。

编辑： 我可以在这里使用柜台：任何 cmets？

     BEGIN  
        -- DECLARE bDone INT;
        -- DECLARE bDone1 INT;

        DECLARE i INT;

       DECLARE var2 varCHAR(255);    -- or approriate type
       DECLARE Var1 INT;
       DECLARE cVar1 VARCHAR(250);

       DECLARE curs1 CURSOR FOR  SELECT trim(concat(t.Titel," ",t.Untertitel)) as scopusti FROM tscopus t ;
       DECLARE curs CURSOR FOR  SELECT recid as BIOTIrecid, replace(replace(BIOGRAPHYTITLE," [in SCOPUS]",""),"[SIMILAR]","") as bioti FROM tBIO ;
       DECLARE CONTINUE HANDLER FOR NOT FOUND SET bDone = 1;
       #DECLARE curs1 CURSOR FOR  SELECT trim(concat(t.Titel," ",t.Untertitel)) as scopusti FROM tscopus t ;
       #DECLARE CONTINUE HANDLER FOR NOT FOUND SET bDone = 1;

       DROP  TABLE IF EXISTS LDResults;
        CREATE TABLE `LDResults` (
       `BIOGRAPHYTITLE` varchar(255) DEFAULT NULL,
       `recid` int(11) NOT NULL AUTO_INCREMENT,
       `BIOTIrecid` int(11) default NULL,
       `LD` varchar(255) DEFAULT NULL,
       `ScopusTI` varchar(255) DEFAULT NULL,
       PRIMARY KEY (`recid`)
        ) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;


        OPEN curs1;
        SET i = 0;

        SET bDone1 = 0;
        -- ---------------- run all rows for scopusti
        REPEAT
            FETCH curs1 into cvar1;

         set i=(i+1);
        -- -----------------------------------------
            OPEN curs;

            SET bDone = 0;
            -- ----- run all COLUMNs for biographytitle
            REPEAT
                FETCH curs INTO var1, var2;
                INSERT INTO LDResults (`BIOGRAPHYTITLE`, `BIOTIrecid`, `LD`, `ScopusTI`) VALUES (var2, var1, LEVENSHTEIN(var2,cvar1), cvar1);
            UNTIL bDone END REPEAT;
        -- --------------------------------------------
        CLOSE curs;

        UNTIL (i >= 2) END REPEAT;


       CLOSE curs1;
       SELECT * FROM LDResults;
     END

【参考方案1】：

我的意思是你可以通过下一个方法使用 CROSS JOIN 在你的代码中没有循环。 CROSS JOIN 按定义返回两个表行结果的乘积。 因此，您可以使用此结果，并在进行一些数据操作后将结果插入到新表中，例如：

DROP  TABLE IF EXISTS LDResults;
CREATE TABLE `LDResults` (
   `BIOGRAPHYTITLE` varchar(255) DEFAULT NULL,
   `recid` int(11) NOT NULL AUTO_INCREMENT,
   `BIOTIrecid` int(11) default NULL,
   `LD` varchar(255) DEFAULT NULL,
   `ScopusTI` varchar(255) DEFAULT NULL,
   PRIMARY KEY (`recid`)
) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;

INSERT INTO LDResults (`BIOGRAPHYTITLE`, `BIOTIrecid`, `LD`, `ScopusTI`)
SELECT bioti, BIOTIrecid, LEVENSHTEIN(bioti,scopusti), scopusti
FROM (
    SELECT 
        replace(replace(BIO.BIOGRAPHYTITLE," [in SCOPUS]",""),"[SIMILAR]","") as bioti,
        BIO.recid as BIOTIrecid,
        trim(concat(scopus.Titel," ",scopus.Untertitel)) as scopusti 
    FROM scopus
    CROSS JOIN BIO
) tbl;