pl / sql：将行聚合成varchar？

Question

SELECT concat(concat('m.', COLUMN_NAME), concat(' = mtf.', COLUMN_NAME)) A
 FROM all_tab_columns
where table_name like 'T_EMPLOYEE' 

我得到了结果：

如何将AND和行聚合到varchar中作为下面的预期结果：

m.a_emp_id = mft.a_emp_id AND m.a_emp_name = mft.a_emp_name
AND m.a_emp_sal = mft.a_emp_sal AND m.a_emp_dept = mft.a_emp_dept
AND m.a_emp_status = mft.a_emp_status

Answer 1

  

试试这个。这可能有所帮助。

-------------------------------PLSQL Starts-----------------------------------------

set serveroutput on;
DECLARE
lv_cond LONG;
BEGIN
FOR i IN (
SELECT
  CASE
    WHEN ROWNUM =1
    THEN 'WHERE '
      ||concat(concat('m.', COLUMN_NAME), concat(' = mtf.', COLUMN_NAME))
    ELSE 'AND '
      ||concat(concat('m.', COLUMN_NAME), concat(' = mtf.', COLUMN_NAME))
  END col1
FROM all_tab_columns
WHERE table_name = 'EMP_V1') LOOP
lv_cond:=lv_cond||' '||i.col1;
END LOOP;
dbms_output.put_line(lv_cond);
END;

-------------------------------PLSQL Ends-----------------------------------------

SELECT
  CASE
    WHEN ROWNUM =1
    THEN 'WHERE '
      ||concat(concat('m.', COLUMN_NAME), concat(' = mtf.', COLUMN_NAME))
    ELSE 'AND '
      ||concat(concat('m.', COLUMN_NAME), concat(' = mtf.', COLUMN_NAME))
  END
FROM all_tab_columns
WHERE table_name = 'EMP_V1' ;

---------------------------------OUTPUT---------------------------------------------

COL1
WHERE m.EMPNO = mtf.EMPNO
AND m.ENAME = mtf.ENAME
AND m.JOB = mtf.JOB
AND m.MGR = mtf.MGR
AND m.HIREDATE = mtf.HIREDATE
AND m.SAL = mtf.SAL
AND m.COMM = mtf.COMM
AND m.DEPTNO = mtf.DEPTNO
AND m.NEWADD = mtf.NEWADD
------------------------------------------------------------------------------------

Answer 2

自11G以来，您可以使用LISTAGG功能。

SELECT LISTAGG(
         'm.' || COLUMN_NAME || ' = ' || 'mtf.' || COLUMN_NAME,
         CHR(13) || CHR(10) || 'AND ')
       WITHIN GROUP (ORDER BY COLUMN_ID)  A
FROM all_tab_columns
where table_name like 'T_EMPLOYEE' 

• 我使用||进行varchar连接（对我来说看起来更干净）。
• CHR(13) || CHR(10)是CRLF
• WITHIN GROUP (ORDER BY COLUMN_ID)指定收集行以进行连接的顺序