Question

我正在进行换位，并查看某列是否存在与其他表完全相同的值。示例：

tableA: id = 10, col = abc , value = 10

tableB: id = 10, abc = 10

我有以下代码：

declare
  TYPE  t_my_list is record(id VARCHAR2(4000),col VARCHAR2(4000),val VARCHAR2(4000));
  Type list_3STR is table of t_my_list;

  v_stmt VARCHAR2(32000) := 'SELECT id, col, val FROM userA.tableA';
  v_lstmt VARCHAR2(32000);
  v_ret list_3STR := list_3STR();      
  cDel   number; 
begin
   EXECUTE IMMEDIATE v_stmt BULK COLLECT INTO v_ret;  

    for i in v_ret.first..v_ret.last loop
    --DBMS_OUTPUT.PUT_LINE('ID: '||v_ret (i).id||', COL: '||v_ret (i).col||', VAL: '||v_ret (i).val);

        v_lstmt := 'SELECT count(*) FROM userB.tableB WHERE NVL(cast('||v_ret (i).col||' as Varchar2(100)), ''<null>'') in ('''||v_ret (i).val||''', ''<null>'') and ID = '''||v_ret (i).id||''' ';
        DBMS_OUTPUT.PUT_LINE(v_lstmt);
        EXECUTE IMMEDIATE v_lstmt INTO cDel;

         If cDel > 0 Then
          DBMS_OUTPUT.PUT_LINE('delete row from userA.tableA')
         End if;

    end loop;

DBMS_OUTPUT.PUT_LINE('v_ret = '||v_ret.count);   
end;

我必须考虑 5种情况：

userA.tableA到userB.tableB

从NULL到NULL = 1-删除值
从NULL到DATA = 0-不删除
相同的DATA到DATA = 1-删除
将diffrent数据更改为diffrent数据= 0-不会删除
数据为NULL = 0 =-未删除

我的代码适用于情况1至4。如何解决第5个问题？

更新：案例示例：

1. 
id = 10, col = test, val = null
id = 10, test = null

2.
id = 10, col = test, val = null
id = 10, test = 99

3.
id = 10, col = test, val = 99
id = 10, test = 99

4.
id = 10, col = test, val = 5
id = 10, test = 99

5.
id = 10, col = test, val = 4
id = 10, test = null

Answer 1

我这样做的方法（如果我绝对必须这样做）是找出需要与表b中的哪些列进行比较，然后您可以算出表a中的值可以用来与这些列进行比较。

一旦有了（通过查询user_tables（或根据需要all_tables / dba_tables）以检索相关列），则可以生成一个join子句。

join子句需要检查两个列是否为空或两个列具有相同的非空值。

一旦有了，您就可以在merge语句中使用它来删除符合联接条件的行。为此，我们首先更新匹配的行（为了使这些行在下一步中被删除显示，我们需要这样做），然后将其删除。

这是一个有效的测试用例：

设置：

create table a (id integer, col varchar2(30), val number, constraint a_pk primary key (id, col));

create table b (id integer, abc number, test number, xyz number, constraint b_pk primary key (id));

insert into a (id, col, val)
select 10, 'test', null from dual union all
select 11, 'test', null from dual union all
select 12, 'test', 99 from dual union all
select 13, 'test', 5 from dual union all
select 14, 'test', 4 from dual union all
select 10, 'abc', 1 from dual union all
select 10, 'xyz', 7 from dual union all
select 11, 'abc', 4 from dual union all
select 11, 'xyz', 6 from dual union all
select 12, 'abc', 12 from dual union all
select 12, 'efg', 30 from dual union all
select 13, 'abc', 3 from dual union all
select 13, 'xyz', 5 from dual union all
select 14, 'abc', 8 from dual union all
select 14, 'xyz', 9 from dual;

insert into b (id, abc, test, xyz)
select 10, 1, null, 7 from dual union all
select 11, 4, 99, 8 from dual union all
select 12, 11, 99, 30 from dual union all
select 13, 1, 5, 5 from dual union all
select 14, 1, null, 7 from dual;

commit;

我们希望行保留在表a中

select a.*
from   a tgt
        full outer join b src on (tgt.id = src.id
      and (1 = 0
           or (upper(tgt.col) = 'ABC' and (tgt.val = src.ABC or (tgt.val is null and src.ABC is null)))
           or (upper(tgt.col) = 'TEST' and (tgt.val = src.TEST or (tgt.val is null and src.TEST is null)))
           or (upper(tgt.col) = 'XYZ' and (tgt.val = src.XYZ or (tgt.val is null and src.XYZ is null)))))
where tgt.id is not null and src.id is NULL
ORDER BY a.id, a.col;

ID COL  VAL
-- ---- ---
11 test    
11 xyz    6
12 abc   12
12 efg   30
13 abc    3
14 abc    8
14 test   4
14 xyz    9

运行代码

set serveroutput on

declare
  v_sql clob;
begin
  v_sql := 'merge into a tgt' || chr(10) ||
           '  using  b src' || chr(10) ||
           '  on (tgt.id = src.id' || chr(10) ||
           '      and (1 = 0';

  -- Generate the join conditions
  for rec in (select '           or (upper(tgt.col) = '''||column_name||''' and (tgt.val = src.'||column_name||' or (tgt.val is null and src.'||column_name||' is null)))' join_condition
              from   user_tab_columns
              where  table_name = 'B'
              and    column_name != 'ID')
  loop
    v_sql := v_sql || chr(10) || rec.join_condition;
  end loop;

  v_sql := v_sql || '))' || chr(10) ||
                    'when matched then' || chr(10) || -- we only care about rows that match on the join clause
                    '  update set tgt.col = tgt.col' || chr(10) || -- we need to physically update those rows, or the delete clause won't see them.
                    '  delete where 1=1'; -- we need to have the where clause here, but we're deleting all rows that were updated in the previous step, hence 1=1 which is always true.

  dbms_output.put_line (v_sql||';');

  execute immediate v_sql;
end;
/

语句的dbms_output

merge into a tgt
  using  b src
  on (tgt.id = src.id
      and (1 = 0
           or (upper(tgt.col) = 'ABC' and (tgt.val = src.ABC or (tgt.val is null and src.ABC is null)))
           or (upper(tgt.col) = 'TEST' and (tgt.val = src.TEST or (tgt.val is null and src.TEST is null)))
           or (upper(tgt.col) = 'XYZ' and (tgt.val = src.XYZ or (tgt.val is null and src.XYZ is null)))))
when matched then
  update set tgt.col = tgt.col
  delete where 1=1;

检查是否有我们希望保留的列

select *
from   a
order by id, col;

ID COL  VAL
-- ---- ---
11 test    
11 xyz    6
12 abc   12
12 efg   30
13 abc    3
14 abc    8
14 test   4
14 xyz    9

但是，如果您对此事有任何选择，我将认真，认真地请您重新考虑此设计。

在表a中具有键值是使用表B更新表的一种非常奇怪的方法，并且您已经发现，这样做会使最简单的事情变得非常棘手。

列换位到Oracle（pl / sql，sql）

1 个答案: