Question

我有两个表..在输出结果中我想合并两者的数据。所以假设我必须使用UNION语句。我在结果集中需要什么：

仅来自TABLE1的第1行和第2行。
来自TABLE2的所有行，其中TABLE2 / COL4 = TABLE1 / COL1在＃1中被选中，（这些是表2中的1和3）
在输出结果中，将COL2中的数据替换为TABLE2行的数据，其中包含来自TABLE1的COL2的数据

TABLE1------------------------------------------
COL1  COL2    COL3
1     aaa1    eee1
2     bbb1    fff1
3     ccc1    ggg1
4     ddd1    hhh1

TABLE2------------------------------------------
COL1  COL2    COL3    COL4
1     aaa2    eee2    1
2     bbb2    fff2    4
3     ccc2    ggg2    1
4     ddd2    hhh2    3

RESULT I NEED-----------------------------------
COL1  COL2    COL3
1     aaa1    eee1
2     bbb1    fff1
1     aaa1    eee2
3     aaa1    ggg2

我需要这样的东西：

SELECT#1 COL1, COL2, COL3 FROM TABLE1 WHERE COL1 IN ('1','2')
UNION ALL
SELECT#2 COL1, COL2 <AS SELECT#1.COL2>, COL3 FROM TABLE2 WHERE <COL4 IN SELECT#1.COL1>

Answer 1

select col1, col2, col3 from table1
WHERE COL1 IN (1,2)
union
select t2.col1,
       coalesce((select col2 from table1
                 WHERE COL1 IN (1,2)
                   AND COL1 = t2.col4),
                t2.col2),
       t2.col3
from table2 t2 join table1 t1 on t1.col1 = t2.col1 and col4 in
  (select col1 from table1 WHERE COL1 IN (1,2))

给我：

SQL>select * from table1
SQL&WHERE COL1 IN (1,2)
SQL&union
SQL&select t2.col1,
SQL&       coalesce((select col2 from table1
SQL&                 WHERE COL1 IN (1,2)
SQL&                   AND COL1 = t2.col4),
SQL&                t2.col2),
SQL&       t2.col3
SQL&from table2 t2 join table1 t1 on t1.col1 = t2.col1 and col4 in
SQL&  (select col1 from table1 WHERE COL1 IN (1,2))
SQL&;

       col1 col2   col3
       ==== ====   ====
          1 aaa1   eee1
          2 bbb1   fff1
          1 aaa1   eee2
          3 aaa1   ggg2

4 rows found

从两个DB2表中提取数据，UNION ALL

1 个答案: