pl/sql ：将行聚合到 varchar 中？

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 中作为以下预期结果：

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

Try this. It may help.

-------------------------------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

从 11G 开始，您可以使用 LISTAGG 函数。

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（对我来说看起来更简洁）。
CHR(13) || CHR(10) 是 CRLF
WITHIN GROUP (ORDER BY COLUMN_ID) 指定为串联收集行的顺序

pl/sql ：将行聚合到 varchar 中？

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