请问下面的查询执行的顺序是什么样的，用什么方法来验证？？？？？？？

Question

SELECT COUNT(*) "total",
SUM(DECODE( TO_CHAR(HIREDATE,'YYYY'),'1980',1,0)) AS "1980",
SUM(DECODE( TO_CHAR(HIREDATE,'YYYY'),'1981',1,0)) AS "1981",
SUM(DECODE( TO_CHAR(HIREDATE,'YYYY'),'1982',1,0)) AS "1982",
SUM(DECODE( TO_CHAR(HIREDATE,'YYYY'),'1983',1,0)) AS "1983",
SUM(DECODE( TO_CHAR(HIREDATE,'YYYY'),'1984',1,0)) AS "1984",
SUM(DECODE( TO_CHAR(HIREDATE,'YYYY'),'1985',1,0)) AS "1985",
SUM(DECODE( TO_CHAR(HIREDATE,'YYYY'),'1986',1,0)) AS "1986",
SUM(DECODE( TO_CHAR(HIREDATE,'YYYY'),'1987',1,0)) AS "1987"
FROM EMP;

Answer 1

你可以用PLSQL Developer中的tools-〉explain plan看下

Answer 2

PL/SQL  可以看执行计划(execution plan)

Answer 3

PLSQL Developer有执行计划也可以借用TOAD 来看执行计划