使用动态列 Oracle SQL 查询的数据

Posted 2023-03-27

【中文标题】使用动态列 Oracle SQL 查询的数据

【英文标题】：Data using Dynamic Column Oracle SQL query

【发布时间】：2018-07-11 04:39:11

【问题描述】：

全部 - 我想在下面使用 Oracle SQL 查询（不是 PL/SQL）来实现。请让我知道它是否可以实现

表 1

Column Name : ONLY_COLUMN

Values: 

COLUMN1

COLUMN5

COLUMN3

表 2

COLUMN1 COLUMN2 COLUMN3 COLUMN4 COLUMN5

V1       V2       V3      V4      V5

---

查询输出

(SELECT_COLUMN_VALUE_FROM_TABLE 1)  (VALUE_FROM_CORRESPONDING_COLUMN_FROM_TABLE 2)

COLUMN1 V1

COLUMN5 V5

COLUMN3 V3

---

【参考方案1】：

只有当列列表固定时，您才能在纯 SQL 中执行此操作，就像您的情况一样。

with tbl1 as (
  select 'COLUMN1' only_column from dual union all
  select 'COLUMN5' only_column from dual union all
  select 'COLUMN3' only_column from dual
),
tbl2 as (
  select 'V1' COLUMN1, 'V2' COLUMN2, 'V3' COLUMN3, 'V4' COLUMN4,'V5' COLUMN5 from dual
)
select only_column,
       case only_column
         when 'COLUMN1' then COLUMN1
         when 'COLUMN2' then COLUMN2
         when 'COLUMN3' then COLUMN3
         when 'COLUMN4' then COLUMN4
         when 'COLUMN5' then COLUMN5
       end res
from   tbl2, tbl1

输出：

ONLY_COLUMN RES
----------
COLUMN1 V1
COLUMN5 V5
COLUMN3 V3

【参考方案2】：

试试这个

create table tst (col varchar2(10));
create table tst1 (c1 varchar2(10), c2 varchar2(10), c3 varchar2(10), c4 varchar2(10), c5 varchar2(10));
insert into tst values ('c1');
insert into tst values ('c5');
insert into tst values ('c3');
insert into tst1 values ('V1', 'V2', 'V3', 'V4', 'V5');

Select tst.col, 
case 
    when tst.col = 'c1' then tst1.c1
    when tst.col = 'c2' then tst1.c2
    when tst.col = 'c3' then tst1.c3
    when tst.col = 'c4' then tst1.c4
    when tst.col = 'c5' then tst1.c5
end as val
From tst, tst1

【参考方案3】：

使用 unpivot，这是非常直接的：

with tbl1 as (
  select 'COLUMN1' only_column from dual union all
  select 'COLUMN5' only_column from dual union all
  select 'COLUMN3' only_column from dual
),
tbl2 as (
  select 'V1' COLUMN1, 'V2' COLUMN2, 'V3' COLUMN3, 'V4' COLUMN4,'V5' COLUMN5 from dual
),
piv2 as (
    select * 
    from   tbl2
    unpivot( val for col in (COLUMN1,COLUMN2,COLUMN3,COLUMN4,COLUMN5))
)
select only_column, val from tbl1,piv2
where piv2.col = tbl1.only_column

结果：

ONLY_COLUMN VAL
----------- ---
COLUMN1     V1
COLUMN3     V3
COLUMN5     V5