WHILE loop in Teradata procedure - sql

Question

I'm trying to write a procedure that concatenates all rows in a table in the case in which the row number is unknown.
I have this code but it is not working.
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
;
I'm getting the following errors:
Syntax error, expected something like ';' between an integer and ','.'.
Unexpected text 'SET'.
New code, as suggested by dnoeth.
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;
Now I get this error:
[3706] Syntax error: Column name list shorter than select list.
EDIT 2:
I have now rewritten it like this:
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;
But I'm getting the following error:
CALL Failed. [3813] The positional assignment list has too many values.
I have tried modifying it but when I delete one value than it says that column name list is longer then the select list.

Answer 1

This is translated to valid syntax for Teradata/Standard SQL (and a bit simplified):
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
;
What's the content of tableWithSQLStmnts?
Why do you want a single line? There are simpler ways to get a kind of LISTAGG.
Edit:
Based on your comments (here and on Teradata's Developer Exchange) it looks like you want to apply some kind of count to every column. But then you don't need the MAX/CASE/ROW_NUMBER, simply concat all rows for a table and then execute it. This counts NULLs in every column of a table:
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');