Question

我正在尝试在一个月内每天运行查询。本月第一天的查询部分看起来像这样，并且有效：

CASE 
WHEN CONCAT(
    Shifts.d1a,
    Shifts.d1b, 
    Shifts.d1c, 
    Shifts.d1d, 
    Shifts.d1e, 
    Shifts.d1f) = "" THEN "-"
ELSE
  CONCAT (
    IF (Shifts.d1a='Yes','A',''),
    IF (Shifts.d1b='Yes','B',''),
    IF (Shifts.d1c='Yes','C',''),
    IF (Shifts.d1d='Yes','D',''),
    IF (Shifts.d1e='Yes','E',''),
    IF (Shifts.d1f='Yes','F','')
    ) END AS d1,

该月的第二天看起来是一样的，除了表引用的所有“d1”部分都是“d2”，而“END AS d1”将是“END AS d2”。

我继承了表结构;每个d [n] [x]得到“是”或“”的值。没有涉及空值。目标是在一天内单独采用现场物品 - 即d [n] a，d [n] b，d [n] c等，并将它们连接成（例如）“ABF”，用于每个具有“是”的字段值，如果所有字段都为空，则在列d [n]中生成连字符。

就像我说的，如果我运行31次几乎完全相同的代码，这就有效。这让我感到丑陋和不必要。但是我遇到了明显的问题，即在SELECTs中使用串联字符串作为列名，以及在输出中使用变量作为列别名的一部分。所以这不起作用：

BEGIN
  DECLARE vcounter INT DEFAULT 0;
  DECLARE vcolumn VARCHAR (10);
  DECLARE vcolumna VARCHAR (64);
  DECLARE vcolumnb VARCHAR (64);
  DECLARE vcolumnc VARCHAR (64);
  DECLARE vcolumnd VARCHAR (64);
  DECLARE vcolumne VARCHAR (64);
  DECLARE vcolumnf VARCHAR (64);
shift_loop: REPEAT
SET vcounter = vcounter + 1;
SET vcolumn = CONCAT ('d',vcounter);
SET vcolumna = CONCAT ('Shift.',vcolumn,'a');
SET vcolumnb = CONCAT ('Shift.',vcolumn,'b');
SET vcolumnc = CONCAT ('Shift.',vcolumn,'c');
SET vcolumnd = CONCAT ('Shift.',vcolumn,'d');
SET vcolumne = CONCAT ('Shift.',vcolumn,'e');
SET vcolumnf = CONCAT ('Shift.',vcolumn,'f');
SELECT 
  CASE 
   WHEN CONCAT(
        vcolumna,
        vcolumnb,
        vcolumnc,
        vcolumnd,
        vcolumne,
        vcolumnf) = '' THEN '-'
    ELSE 
        CONCAT(
        vcolumna,
        vcolumnb,
        vcolumnc,
        vcolumnd,
        vcolumne,
        vcolumnf
        ) 
        END
          AS vcolumn;
UNTIL vcounter = 1
END REPEAT;
END

是的，我知道程序中的CASE语句是不必要的 - 我可以将最终CONCAT的结果分配给变量并针对空值进行测试。我刚刚离开了这个，以便更好地了解我想要做的事情。

结果是，对于每一行，我得到一个名为“vcounter”的列，其内容为“Shift.d1aShift.d1bShift.d1c”等。有没有人有任何建议？

已添加

好的，谢谢，我查看了建议的答案，但我无法弄清楚如何使用我需要的WHILE语句。这是我将代码更改为：

 BEGIN  
 SET @vcounter = 0;  
 SET @vcounter = @vcounter + 1;  
 SET @vtable = 'Table_X';  
 SET @vcolumn = CONCAT ('d',@vcounter);  
 SET @vcolumna = CONCAT (@vtable,'.',@vcolumn,'a');  
 SET @vcolumnb = CONCAT (@vtable,'.',@vcolumn,'b');  
 SET @vcolumnc = CONCAT (@vtable,'.',@vcolumn,'c');  
 SET @vcolumnd = CONCAT (@vtable,'.',@vcolumn,'d');  
 SET @vcolumne = CONCAT (@vtable,'.',@vcolumn,'e');   
 SET @vcolumnf = CONCAT (@vtable,'.',@vcolumn,'f');  
 SET @vshifts = CONCAT  
 (@vcolumna,',',@vcolumnb,',',@vcolumnc,',',@vcolumnd,',',@vcolumne,',',@vcolumnf);  
 SET @vquery = CONCAT ('SELECT CASE WHEN CONCAT (',  
                  @vshifts,  
                  ') ="" THEN "-" ELSE   
                  CONCAT (IF(',@vcolumna,' = "Yes","A",""),  
                          IF(',@vcolumnb,' = "Yes","B",""),  
                          IF(',@vcolumnc,' = "Yes","C",""),  
                          IF(',@vcolumnd,' = "Yes","D",""),  
                          IF(',@vcolumne,' = "Yes","E",""),  
                          IF(',@vcolumnf,' = "Yes","F","")  
                  )END AS ',@vcolumn,' FROM ',@vtable);  
 PREPARE stmt FROM @vquery;  
 EXECUTE stmt;  
 END

这适用于一天。问题是，无论我在何处插入WHILE或REPEAT语句，都会得到不好的结果。我发现的最接近的结果会产生看起来像

的结果

 d1  
 D  
 F  
 A  
 B  

 d2  
 A  
 AB  
 C  
 -

等。我想要的是

 d1    d2  
 D     A
 F     AB
 A     C
 B     -

我显然对我在这里所做的事情了解不多，所以我非常感谢任何人都可以提供帮助。感谢。

Answer 1

好的，我自己解决了。这是有效的：

 BEGIN
 SET @vcounter = 0;
 SET @vtable = 'tablename';
 SET @vquery = 'SELECT
  last_name As Last_Name,
  first_name As First_Name, ';
 shift_loop: REPEAT
 SET @vcounter = @vcounter + 1;
 SET @vcolumn = CONCAT ('d',@vcounter);
 SET @vcolumna = CONCAT (@vcolumn,'a');
 SET @vcolumnd = CONCAT (@vcolumn,'b');
 SET @vcolumnp = CONCAT (@vcolumn,'c');
 SET @vcolumne = CONCAT (@vcolumn,'d');
 SET @vcolumnt = CONCAT (@vcolumn,'e');
 SET @vcolumns = CONCAT (@vcolumn,'f');
 SET @vshifts = CONCAT (@vcolumna,',',@vcolumnb,',',@vcolumnc,',',@vcolumnd,',',@vcolumne,',',@vcolumnf);
 SET @vquery = CONCAT (@vquery,' CASE WHEN CONCAT (',
                       @vshifts,
                       ') ="" THEN "-" ELSE 
                       CONCAT (IF(',@vcolumna,' = "Yes","A",""),
                              IF(',@vcolumnb,' = "Yes","B",""),
                              IF(',@vcolumnc,' = "Yes","C",""),
                              IF(',@vcolumnd,' = "Yes","D",""),
                              IF(',@vcolumne,' = "Yes","E",""),
                                  IF(',@vcolumnf,' = "Yes","F","")
                       ) END AS ',@vcolumn,',');
 Until @vcounter = 31
 END REPEAT;
 SET @vquery = CONCAT (
     @vquery,'
     comment AS Comment,
     _submitted_ AS Submitted
     FROM ',@vtable);
 PREPARE stmt FROM @vquery;
 EXECUTE stmt;
 DEALLOCATE PREPARE stmt;
 END

列名称，列别名

1 个答案: