Answer 1: SELECT employeeID, dept, salary
FROM employee
WHERE (dept, salary) = (SELECT dept, salary
FROM employee
WHERE employeeID = '100');
--------------------------------------------------------------
Answer 2:SELECT employeeID, dept, salary
FROM employee
WHERE dept = (SELECT dept
FROM employee
WHERE employeeID = '100')
AND
salary = (SELECT salary
FROM employee
WHERE employeeID = '100');
--------------------------------------------------------------
Answer 3:SELECT partID, description, unit_cost, sell_price
FROM parts
WHERE (unit_cost, sell_price) = (SELECT unit_cost, sell_price
FROM parts
WHERE partID = '1234');
--------------------------------------------------------------
Answer 4:SELECT partID, description, unit_cost, sell_price
FROM parts
WHERE unit_cost = (SELECT unit_cost
FROM parts
WHERE partID = '1234')
AND
sell_price = (SELECT sell_price
FROM parts
WHERE partID = '1234');
Question:
Identify the two statements that contain pairwise multi-column subsqueriesA.Answer 1
B.Answer 2
C.Answer 3
D.Answer 4
这个题目的意思看不太明白,会的帮忙解决下,答案我知道的,是A,C
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=====================================
A: WHERE (dept, salary) = (SELECT dept, salary
C: WHERE (unit_cost, sell_price) = (SELECT unit_cost, sell_price
成对的,多字段,子查询
contain pairwise multi-column subsqueries
连在一起什么意思?
找出两个包含多字段子查询的语句,相比两个子select,一个子select的性能肯定要好!
pairwise不知道是什么意思。。查下金山词霸吧!
subsqueries 子查询
pairwise 成对 本题是要求有2个行(字段)的多行
现在想想 (dept, salary) 和(unit_cost, sell_price)是不是对应所谓的多行呢?!
而B和D则是分别对单个字段判断 再 AND
以下翻译,谨供参考~~
意思是:找出下面含有对应两行的(多行)子查询的SQL语句~~