Question

这是我实际代码的一个简单的条带，但我想不知道如何做到这一点，所以我可以应用它。我有这样的代码：

declare

use_t3 varchar2(1): = 'N'; //Y or N
use_t4 varchar2(1): = 'N'; //Y or N

begin

INSERT INTO MY_BIG_TABLE
SELECT
     t3.qid AS "QID",
    (SELECT t5.flag FROM t5 WHERE(t5.qid = t4.qid)) AS "FLAG"
    FROM
      t1 p,
      t2 pm,
      t3 pms,
      t4 pmo
WHERE
      t1.id = t2.qid
      AND t3.day = 'Monday'
      AND t2.id = t4.pmd_id(+)
      AND t4.date IS NULL
end;

现在我有两个变量：

use_t3
use_t4

如果use_t3和use_t4都等于'Y'（这意味着是，请使用这些表），那么查询应该按照两个表应该使用的完全相同的方式运行（只有use_t1或use_t2可以等于' N'，这意味着总会有一个属于'Y'的人。

如果use_t3 ='N'且use_t4 ='Y'，那么我希望t3.qid列仍然显示但返回null，并且条件为：

t3.day = 'Monday'

不使用。

如果use_t3 ='Y'且use_t4 ='N'，那么我希望“FLAG”列返回空白值和条件：

t2.id = t4.pmd_id(+)
AND t4.date IS NULL

不使用。

我希望这是有道理的。

干杯

Answer 1

要有条件地连接到表，ANSI LEFT JOIN中的case语句应该可以正常工作，只要导出就可以在两个表上使用Left Join。

declare

use_t3 varchar2(1): = 'N'; //Y or N
use_t4 varchar2(1): = 'N'; //Y or N

begin

INSERT INTO MY_BIG_TABLE
SELECT
     t3.qid AS "QID",
    (SELECT T5.FLAG FROM T5 WHERE(T5.QID = T4.QID)) AS "FLAG"
    FROM           T1 /*P*/ 
              JOIN T2 /*PM*/  ON T1.ID = T2.QID
         LEFT JOIN T3 /*pms*/ ON CASE WHEN USE_T3 = 'Y' AND T3.DAY = 'Monday' THEN 1 ELSE 0 END = 1
         LEFT JOIN t4 /*pmo*/ ON CASE WHEN USE_T4 = 'Y' AND T2.ID = T4.PMD_ID AND t4.date IS NULL THEN 1 ELSE 0 END = 1
end;

否则，您可能不得不做多个IF THEN语句来涵盖每个选项。

declare

USE_T3 VARCHAR2(1): = 'N'; --//Y or N
use_t4 varchar2(1): = 'N'; --//Y or N

BEGIN
--If both are 'Y' ---------------------
IF USE_T3 = 'Y' AND USE_T4 = 'Y' then
INSERT INTO MY_BIG_TABLE
SELECT
     t3.qid AS "QID",
    (SELECT t5.flag FROM t5 WHERE(t5.qid = t4.qid)) AS "FLAG"
    FROM
      t1 p,
      t2 pm,
      t3 pms,
      t4 pmo
WHERE
      t1.id = t2.qid
      AND t3.day = 'Monday'
      AND t2.id = t4.pmd_id(+)
      AND T4.DATE IS NULL
END IF;

--If USE_T3 is 'Y' And USE_T4 is 'N' ---------------------
if IF USE_T3 = 'Y' AND USE_T4 = 'N' then
INSERT INTO MY_BIG_TABLE
SELECT
     t3.qid AS "QID",
    NULL AS "FLAG"
    FROM
      t1 p,
      t2 pm,
      t3 pms
WHERE
      t1.id = t2.qid
      AND t3.day = 'Monday'
END IF;

--If USE_T3 is 'N' And USE_T4 is 'Y' ---------------------
IF USE_T3 = 'N' AND USE_T4 = 'Y' then
INSERT INTO MY_BIG_TABLE
SELECT
     NULL AS "QID",
    (SELECT t5.flag FROM t5 WHERE(t5.qid = t4.qid)) AS "FLAG"
    FROM
      t1 p,
      t2 pm,
      t4 pmo
WHERE
      t1.id = t2.qid
      AND t2.id = t4.pmd_id(+)
      AND T4.DATE IS NULL
end if;

end;

Answer 2

你可以使用字符串连接..

    DECLARE

      use_t3 varchar2(1): = 'N'; //Y or N
      use_t4 varchar2(1): = 'N'; //Y or N
      plsql_block VARCHAR2(500);

    BEGIN

      -- Dynamic PL/SQL block invokes insert statement:
      plsql_block := 'INSERT INTO MY_BIG_TABLE ' 
                   ||' SELECT ';

      If use_t3 = 'Y' then
          plsql_block := 
              plsql_block || ' t3.qid AS "QID", ';
      Else
          plsql_block := 
              plsql_block || ' null AS "QID", ';
      End if;

      If use_t4 = 'Y' 
          plsql_block := 
              plsql_block || ' (SELECT t5.flag FROM t5 WHERE(t5.qid = t4.qid)) AS "FLAG"';

      Else
          plsql_block := 
              plsql_block || ' '''' AS "FLAG", ';
      End if;


      plsql_block := plsql_block || ' FROM t1 p, t2 pm ';

      If use_t3 = 'Y' then
          plsql_block := 
              plsql_block || ' ,t3 pms ';
      End if

      If use_t4 = 'Y' then
          plsql_block := 
              plsql_block || ' ,t4 pmo ';
      End if

      plsql_block := plsql_block || ' WHERE t1.id = t2.qid ';

      If use_t3 = 'Y' then
          plsql_block := 
              plsql_block || ' AND t3.day = ''Monday'' ';
      End if

      If use_t4 = 'Y' then
          plsql_block := 
            plsql_block || ' AND t2.id = t4.pmd_id(+) AND t4.date IS NULL ' ;
      End if    

      EXECUTE IMMEDIATE plsql_block;   
   END;

基于变量返回列，但显示空白值并且不使用条件

2 个答案: