Question

你能帮我建一个如下的查询吗？

TABLE_A

id品牌颜色尺码型号yn_buy
1 A蓝色M A -
2灰色X C -
3 B红色X B -
4 C blue S C -

表-B

品牌标准颜色=灰色，尺寸= X
B颜色=红色
C size = M

我想构建一个更新表A的查询，答案应该是：

TABLE_A

id品牌颜色尺码型号yn_buy
1 A蓝色M A N
2灰色X C Y
3 B red X B Y
4 C blue S C N

正如您所看到的那样，“批评”一栏上的数据应该是买或不买的决定因素

我想使用单个合并，如下所示

合并到TABLE_A中使用
（
选择ID，品牌，批判时的情况>然后'Y'ELSE'N'END yn_buy
TABLE_A a
left join TABLE_B b ON a.brand = b.brand
）b
ON（a.id = b.id）
匹配然后更新设置a.yn_buy = b.yn_buy

可以这样做吗？也许使用执行立即，某种绑定...？

谢谢你

Answer 1

如果我在你的特定情况下不遗漏你不需要动态SQL - 你可以简单地改变TABLE_B结构并使用静态MERGE（因为我不知道你的标准有多复杂，这只是一个例子）：

SQL> create table table_a (id, brand, color, size#, model#, tn_buy) as
  2  select 1,    'A',          'blue',             'M',           'A', cast(null as varchar2(3)) from dual union all
  3  select 2,    'A',         'grey',              'X',          'C', cast(null as varchar2(3)) from dual union all
  4  select 3,    'B',         'red',               'X',           'B', cast(null as varchar2(3)) from dual union all
  5  select 4,    'C',        'blue',              'S',           'C', cast(null as varchar2(3)) from dual
  6  /

Table screated.

SQL> create table TABLE_B (brand, color, size#)
  2  as
  3  select 'A',          'grey', 'X' from dual union all
  4  select 'B',           'red', null from dual union all
  5  select 'C',          null, 'M' from dual
  6  /

Table created.

SQL> merge into TABLE_A a USING (
  2     select a.id, a.brand, CASE
  3     WHEN a.color = nvl(a.color, a.color) and a.size# = nvl(b.size#,a.size#)
  4     THEN 'Y' ELSE 'N' END yn_buy FROM
  5       TABLE_A a
  6       left join TABLE_B b ON a.brand = b.brand
  7  ) b
  8  ON (a.id = b.id)
  9  WHEN MATCHED THEN UPDATE set a.yn_buy = b.yn_buy
 10  /

4 rows merged.

SQL> select * from table_a order by id;

        ID B COLO S M YN_                                                       
---------- - ---- - - ---                                                       
         1 A blue M A N                                                         
         2 A grey X C Y                                                         
         3 B red  X B Y                                                         
         4 C blue S C N

但是你的标准很难用简单的静态条件实现，那么你可以使用动态SQL：

SQL> create table TABLE_B1 (brand, criteria)
  2  as
  3  select 'A',          q'[color='grey' and size# in ('X','M')]' from dual union all
  4  select 'B',           q'[color = 'red']' from dual union all
  5  select 'C',          q'[size#='M']' from dual
  6  /

Table created.

SQL> update table_a set yn_buy = null;

4 rows updated.

SQL> commit;

Committed.

SQL> begin
  2    for cur in (select brand, criteria from table_b1) loop
  3      execute immediate
  4      'update table_a set yn_buy = case when '||cur.criteria||
  5      q'[ then 'Y' else 'N' end where brand = :1]' using cur.brand;
  6    end loop;
  7  end;
  8  /

PL/SQL procedure completed.

SQL> select * from table_a;

        ID B COLO S M YN_                                                       
---------- - ---- - - ---                                                       
         1 A blue M A N                                                         
         2 A grey X C Y                                                         
         3 B red  X B Y                                                         
         4 C blue S C N

在oracle中构建动态查询

1 个答案: