ORA-01789:query block has incorrect number of result columns

在写一个8张表一起union all 的SQL时，遇到了ORA-01789:query block has incorrect number of result columns

顾名思义，查询块的列数目不相等。

下面的SQL，查询时就会报ORA-01789错误

select empno, ename, job, sal from emp t where t.deptno = 20unionselect empno, ename, sal from emp t where t.deptno = 30

补上第二个块的列，补齐了就可以正常查询了。

select empno, ename, job, sal  from emp t where t.deptno = 20unionselect empno, ename, 'job', sal  from emp t where t.deptno = 30