WHILE循环在Teradata程序

Question

我正试图编写一个过程，在行数未知的情况下连接表中的所有行。

我有这个代码，但它不工作。

CREATE PROCEDURE Test (OUT r VARCHAR(3000)) 

BEGIN 
DECLARE RowCnt INT; 
DECLARE CurrRow INT ; 
SET CurrRow = 1, 
     r = 'SELECT ', 
     RowCnt = (SELECT COUNT(*) 
        FROM tableWithSQLStmnts 
        )  
WHILE CurrRow <= RowCnt DO 
BEGIN 
      SET r = r + 
      CASE WHEN CurrRow = 1 
       THEN 'MAX(CASE Seq WHEN ' + CAST(CurrRow AS VARCHAR) + ' 
           THEN SqlStmnt 
              ELSE SPACE(0) END) + ' + CHAR(13) 
      WHEN i = RowCnt 
      THEN 'MAX(CASE Seq WHEN ' + CAST(CurrRow AS VARCHAR) + ' 
           THEN '' '' + SqlStmnt 
           ELSE SPACE(0) END) ' + CHAR(13) 
      ELSE 'MAX(CASE Seq WHEN ' + CAST(CurrRow AS VARCHAR) + ' 
           THEN '' '' + SqlStmnt 
           ELSE SPACE(0) END) + ' + CHAR(13) 
      END 
      SET CurrRow = CurrRow + 1 ; 
END ; 
SET r = r + ' 
    FROM (SELECT SqlStmnt, 
        ROW_NUMBER() OVER (PARTITION BY TabName ORDER BY SQlStmnt) 
      FROM tableWithSQLStmnts t) D (SqlStmnt, Seq) 
      GROUP BY TabName;' 

END WHILE; 
END 

; 

，我发现了以下错误：

• 语法错误，期望像 ';'在一个整数和'，'。'之间。
• 意外的文字'SET'。

dnoeth建议的新代码。

REPLACE PROCEDURE Test3 (IN TbName VARCHAR(256)) --, OUT r2 VARCHAR(3000)) 

BEGIN 
DECLARE RowCnt INT; 
DECLARE i INT; 
DECLARE CurrRow INT; 
DECLARE r VARCHAR(3000); 
DECLARE r2 VARCHAR(3000); 
SET CurrRow = 1; 
SET r = 'SELECT '; 
SET RowCnt = (SELECT COUNT(*) 
       FROM tableWithSQLStmnts 
       WHERE tabname = :TbName 
      ); 

WHILE CurrRow <= RowCnt DO 
    BEGIN 
     SET r = r || 
    'MAX(CASE Seq WHEN ' || CAST(CurrRow AS VARCHAR(10)) || ' 
      THEN '' , '' || SqlStmnt 
      ELSE '''' END) 
    ' 
     || CASE WHEN CurrRow = RowCnt 
       THEN '' 
       ELSE ' || ' 
     END; 
     SET CurrRow = CurrRow + 1 ; 
    END; 
END WHILE; 

SET r = r || ' 
    FROM (SELECT SqlStmnt, 
        ROW_NUMBER() OVER (PARTITION BY TbName ORDER BY SQlStmnt) 
      FROM tableWithSQLStmnts t) D (SqlStmnt) 
      GROUP BY TbName 
      ;'; 

SET r2 = r; 
CALL dbc.sysexecsql(:r); 
END; 

现在我得到这个错误：

[3706] Syntax error: Column name list shorter than select list. 

编辑2：

我现在已经改写这样的：

REPLACE PROCEDURE Test3 (IN TabName VARCHAR(256)) 
DYNAMIC RESULT SETS 1 
BEGIN 
DECLARE RowCnt INT; 
DECLARE Seq INT; 
DECLARE QRY VARCHAR(3000); 
DECLARE CurrRow INT; 
SET QRY= 'INSERT INTO vt21 SELECT '; 
SET CurrRow = 1; 

CREATE VOLATILE TABLE vt21(QRY VARCHAR(3000)) ON COMMIT PRESERVE ROWS; 
SET RowCnt = (SELECT COUNT(*) 
       FROM TestTable 
       WHERE tabname = :TabName 
      ); 
FOR CurrentRefRow AS SourceCursor CURSOR FOR 
      SELECT SqlStmnt 
      FROM TestTable 
      DO 
WHILE CurrRow <= RowCnt 
DO 
    BEGIN 
     SET QRY = QRY || 
     CASE WHEN CurrRow=1 
     THEN 'MAX(CASE Seq WHEN ' || CAST(CurrRow AS VARCHAR(10)) || ' 
      THEN '' , '' || SqlStmnt 
      ELSE '''' END)  ' 

     WHEN CurrRow < RowCnt 
     THEN ', MAX(CASE Seq WHEN ' || CAST(CurrRow AS VARCHAR(10)) || ' 
      THEN '' , '' || SqlStmnt 
      ELSE '''' END) ' 
     WHEN CurrRow=RowCnt 
     THEN ', MAX(CASE Seq WHEN ' || CAST(CurrRow AS VARCHAR(10)) || ' 
      THEN '' , '' || SqlStmnt 
      ELSE '''' END) ' 
       ELSE ' || ' 
     END; 
        SET CurrRow = CurrRow + 1 ; 
     END; 
     END WHILE; 

SET QRY = QRY || ' 
    FROM (SELECT SqlStmnt, Tabname, 
        ROW_NUMBER() OVER (PARTITION BY TabName ORDER BY SQlStmnt) 
      FROM TestTable t) D (Seq, Tabname, SqlStmnt) 
      GROUP BY TabName 
      ;'; 

EXECUTE IMMEDIATE QRY; 
END FOR; 


BEGIN -- return the result set 
     DECLARE resultset CURSOR WITH RETURN ONLY FOR S1; 
     SET QRY = 'SELECT * FROM vt21;'; 
     PREPARE S1 FROM QRY; 
     OPEN resultset; 
    END; 

DROP TABLE vt21; 
END; 

但我发现了以下错误：

CALL失败。位置分配列表具有太多的值。

我试着修改它，但是当我删除一个值比它说列名称列表更长，然后选择列表。

Answer 1

这被转换为有效的语法为Teradata /标准SQL（以及一些简化）：

REPLACE PROCEDURE Test (OUT r2 VARCHAR(3000)) 

BEGIN 
DECLARE RowCnt INT; 
DECLARE i INT; 

DECLARE CurrRow INT; 
DECLARE r VARCHAR(3000); 

SET CurrRow = 1; 
SET r = 'SELECT '; 
SET RowCnt = (SELECT Count(*) 
       FROM tableWithSQLStmnts 
      ); 

WHILE CurrRow <= RowCnt DO 
    BEGIN 
     SET r = r || 
    'MAX(CASE Seq WHEN ' || Cast(CurrRow AS VARCHAR(10)) || ' 
      THEN '' '' || SqlStmnt 
      ELSE '''' END) 
    ' 
     || CASE WHEN CurrRow = RowCnt 
       THEN '' 
       ELSE ' || ' 
     END; 
     SET CurrRow = CurrRow + 1 ; 
    END; 
END WHILE; 

SET r = r || ' 
    FROM (SELECT department_name--SqlStmnt, 
        ROW_NUMBER() OVER (PARTITION BY TabName ORDER BY SQlStmnt) 
      FROM tableWithSQLStmnts t) D (SqlStmnt, Seq) 
      GROUP BY TabName 
      ;'; 

SET r2 = r; 
END 
; 

什么的tableWithSQLStmnts的内容？

为什么你想要一条线？有更简单的方法来获得一种LISTAGG。

编辑：

根据您的意见（这里和Teradata的开发者交流），它看起来像你想要某种计数适用于每一列。但是，您不需要MAX/CASE/ROW_NUMBER，只需将所有行连接为一个表，然后执行它。这种计算空值在表中的每一列：

REPLACE PROCEDURE Test3 (IN DBName VARCHAR(128),IN TabName VARCHAR(128)) 
DYNAMIC RESULT SETS 1 
BEGIN 

    DECLARE QRY VARCHAR(3000); 

    CREATE VOLATILE TABLE vt21(col VARCHAR(128) CHARACTER SET Unicode, NullCnt BIGINT) ON COMMIT PRESERVE ROWS; 

    SET QRY = 'INSERT INTO vt21 '; 

    FOR c AS 
     SELECT DatabaseName, TableName, ColumnName, 
     Row_Number() 
     Over (PARTITION BY tablename 
       ORDER BY columnname) AS rn, 
     Count(*) 
     Over (PARTITION BY tablename) AS Cnt 
     FROM dbc.ColumnsV 
     WHERE DatabaseName = :DBName 
     AND TableName = :TabName 
    DO 
     SET QRY = QRY 
     || 'SELECT ''' || c.ColumnName 
     || ''', COUNT(CASE WHEN ' || c.columnname 
     || ' IS NULL THEN 1 END) FROM ' 
     || c.DatabaseName || '.' || c.TableName 
     || CASE WHEN c.rn = c.Cnt -- last row 
       THEN ';' 
       ELSE ' UNION ALL ' 
      END; 

    END FOR; 

    EXECUTE IMMEDIATE QRY; 

    BEGIN -- return the result set 
     DECLARE resultset CURSOR WITH RETURN ONLY FOR S1; 
     SET QRY = 'SELECT * FROM vt21;'; 
     PREPARE S1 FROM QRY; 
     OPEN resultset; 
    END; 

    DROP TABLE vt21; 

END; 

CALL Test3('dbc', 'dbcinfoV');