使用if-else或not在oracle sql中进行条件连接

如何在oracle sql中实现这一点我尝试了不同的方法。这里我提供了if-else查询，以了解我需要执行什么

if(SELECT SLS_CONT_NO FROM GL WHERE GL.INVNO = '67883' AND GL.CUST_ID = '14714') is not null
then
SELECT DISTINCT M.NAME FROM GL 
JOIN SALES_CONT SLS ON GL.SLS_CONT_NO = SLS.SLS_CONT_NO   
JOIN MARKETER M ON M.MKTRINIT = SLS.MKTRINIT
WHERE GL.INVNO = '67883' AND GL.CUST_ID = '14714';
ELSE
SELECT DISTINCT M.NAME FROM GL 
JOIN TANK TA ON GL.DEST_TANK=TA.TANK_NO  
JOIN MARKETER M ON M.MKTRINIT = TA.MKTRINIT
WHERE GL.INVNO = '67883' AND GL.CUST_ID = '14714';
end if

---

您可以使用CASE WHEN语句

SELECT CASE WHEN a.SLS_CONT_NO IS NOT NULL 
            THEN (SELECT DISTINCT M.NAME
                    FROM GL b
                    JOIN SALES_CONT SLS
                      ON b.SLS_CONT_NO = SLS.SLS_CONT_NO   
                    JOIN MARKETER M
                      ON M.MKTRINIT = SLS.MKTRINIT
                   WHERE b.INVNO = '67883' AND b.CUST_ID = '14714')
            ELSE (SELECT DISTINCT M.NAME
                    FROM GL c
                    JOIN TANK TA
                      ON c.DEST_TANK = TA.TANK_NO  
                    JOIN MARKETER M
                      ON M.MKTRINIT = TA.MKTRINIT
                   WHERE c.INVNO = '67883' AND c.CUST_ID = '14714')
             END AS NAME
 FROM GL a
WHERE a.INVNO = '67883'
  AND a.CUST_ID = '14714';

---

您可以使用CASE WHEN语句

SELECT CASE WHEN a.SLS_CONT_NO IS NOT NULL 
            THEN (SELECT DISTINCT M.NAME
                    FROM GL b
                    JOIN SALES_CONT SLS
                      ON b.SLS_CONT_NO = SLS.SLS_CONT_NO   
                    JOIN MARKETER M
                      ON M.MKTRINIT = SLS.MKTRINIT
                   WHERE b.INVNO = '67883' AND b.CUST_ID = '14714')
            ELSE (SELECT DISTINCT M.NAME
                    FROM GL c
                    JOIN TANK TA
                      ON c.DEST_TANK = TA.TANK_NO  
                    JOIN MARKETER M
                      ON M.MKTRINIT = TA.MKTRINIT
                   WHERE c.INVNO = '67883' AND c.CUST_ID = '14714')
             END AS NAME
 FROM GL a
WHERE a.INVNO = '67883'
  AND a.CUST_ID = '14714';

---

考虑使用

EXISTS/notexists

子句进行

UNION

查询，其中至少一个

SELECT

语句将返回：

SELECT M.NAME FROM GL 
JOIN SALES_CONT SLS ON GL.SLS_CONT_NO = SLS.SLS_CONT_NO   
JOIN MARKETER M ON M.MKTRINIT = SLS.MKTRINIT
WHERE GL.INVNO = '67883' AND GL.CUST_ID = '14714'
  AND EXISTS (SELECT SLS_CONT_NO FROM GL 
              WHERE GL.INVNO = '67883' AND GL.CUST_ID = '14714')

UNION

SELECT M.NAME FROM GL 
JOIN TANK TA ON GL.DEST_TANK = TA.TANK_NO  
JOIN MARKETER M ON M.MKTRINIT = TA.MKTRINIT
WHERE GL.INVNO = '67883' AND GL.CUST_ID = '14714'
  AND NOT EXISTS (SELECT SLS_CONT_NO FROM GL 
                  WHERE GL.INVNO = '67883' AND GL.CUST_ID = '14714')

---

考虑使用

EXISTS/notexists

子句进行

UNION

查询，其中至少一个

SELECT

语句将返回：

SELECT M.NAME FROM GL 
JOIN SALES_CONT SLS ON GL.SLS_CONT_NO = SLS.SLS_CONT_NO   
JOIN MARKETER M ON M.MKTRINIT = SLS.MKTRINIT
WHERE GL.INVNO = '67883' AND GL.CUST_ID = '14714'
  AND EXISTS (SELECT SLS_CONT_NO FROM GL 
              WHERE GL.INVNO = '67883' AND GL.CUST_ID = '14714')

UNION

SELECT M.NAME FROM GL 
JOIN TANK TA ON GL.DEST_TANK = TA.TANK_NO  
JOIN MARKETER M ON M.MKTRINIT = TA.MKTRINIT
WHERE GL.INVNO = '67883' AND GL.CUST_ID = '14714'
  AND NOT EXISTS (SELECT SLS_CONT_NO FROM GL 
                  WHERE GL.INVNO = '67883' AND GL.CUST_ID = '14714')

---

是否尝试union或left join（）或nvl（）？是否尝试union或left join（）或nvl（）？每个子查询必须返回一行。否则，查询将不会运行。每个子查询必须返回一行。否则您的查询将无法运行。UNION返回一组唯一的记录，因此不需要使用DISTINCT。@APC…正确。我没有仔细查看就保留了OP的原始查询。UNION返回一组唯一的记录，因此不需要使用DISTINCT。@APC…正确。我没有仔细看就保留了OP的原始查询。