动态游标和 WHERE 子句 Teradata

Question

我正在尝试编写一个过程，其中数据库名称是动态的并且取自 where 子句。到目前为止我得到了这个：

CREATE PROCEDURE Test

(IN DBName VARCHAR(100), OUT RowCount DEC(10,2))

BEGIN

DECLARE SqlStr VARCHAR(1000);

DECLARE C1 CURSOR FOR S1;

SET SqlStr = 'SELECT count(*) FROM '|| DBNAME || '.MyTable ';

PREPARE S1 FROM SqlStr;

OPEN C1 USING DBName;

FETCH C1 INTO RowCount;

CLOSE C1;

END;

我现在需要添加如下内容：

WHERE DBName = (SELECT 'firstpart||EnvName||' FROM EnvTable 
WHERE EnvName = (SELECT EnvName FROM EnvTable WHERE Flag = 1 AND Priority = (SELECT MIN(Priority) FROM EnvTable))

有什么想法吗？我可以在调用过程时添加这个吗？

Answer 1

听起来你只需要一个变量来让它更动态：

CREATE PROCEDURE Test

(OUT RowCount DEC(10,2))

BEGIN

    DECLARE SqlStr VARCHAR(1000);
    DECLARE DBName VARCHAR(100);
    DECLARE C1 CURSOR FOR S1;

    /*Get your DBName variable loaded using SELECT INTO*/   
    SELECT 'firstpart' || EnvName INTO DBName
    FROM EnvTable 
    WHERE Flag = 1 AND Priority = (SELECT MIN(Priority) FROM EnvTable);

    /*and continue what you were doing*/
    SET SqlStr = 'SELECT count(*) FROM '|| DBName || '.MyTable ';

    PREPARE S1 FROM SqlStr;

    OPEN C1 USING DBName;

        FETCH C1 INTO RowCount;

    CLOSE C1;

END;

我不确定你想用 firstpart||envname 做什么，但这应该让你大致了解。本质上，您只需要编写一个 sql 语句来生成 dbname 变量，然后在第二个查询中使用它。

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