Mysql 使用两个子查询的SQL
我正在学习SQL子查询。下面是我在书中使用的子查询：Mysql 使用两个子查询的SQL,mysql,sql,subquery,Mysql,Sql,Subquery,我正在学习SQL子查询。下面是我在书中使用的子查询： SELECT account_id, product_cd, cust_id FROM account WHERE open_branch_id = ( SELECT branch_id FROM branch WHERE name = 'Woburn Branch' ) AND open_emp_id IN ( SELECT emp_id FROM employee WHERE title =
SELECT account_id, product_cd, cust_id
FROM account
WHERE open_branch_id = (
SELECT branch_id
FROM branch
WHERE name = 'Woburn Branch'
) AND open_emp_id IN (
SELECT emp_id
FROM employee
WHERE title = 'Teller' OR title = 'Head Teller'
);
+------------+------------+---------+
| account_id | product_cd | cust_id |
+------------+------------+---------+
| 1 | CHK | 1 |
| 2 | SAV | 1 |
| 3 | CD | 1 |
| 4 | CHK | 2 |
| 5 | SAV | 2 |
| 17 | CD | 7 |
| 27 | BUS | 11 |
+------------+------------+---------+
和子句以及在中打开\emp\u id的原因
我注意到这一点
SELECT account_id, product_cd, cust_id
FROM account
WHERE open_branch_id = (
SELECT branch_id
FROM branch
WHERE name = 'Woburn Branch'
)
您将得到与上面相同的结果。有谁能向我解释一下
子句中最后一个和open\u emp\u id背后的原因，以及省略它会如何影响最终结果
子查询中使用的表：
账表
+------------+------------+---------+------------+------------+--------------------+--------+----------------+-------------+---------------+-----------------+
| account_id | product_cd | cust_id | open_date | close_date | last_activity_date | status | open_branch_id | open_emp_id | avail_balance | pending_balance |
+------------+------------+---------+------------+------------+--------------------+--------+----------------+-------------+---------------+-----------------+
| 1 | CHK | 1 | 2000-01-15 | NULL | 2005-01-04 | ACTIVE | 2 | 10 | 1057.75 | 1057.75 |
| 2 | SAV | 1 | 2000-01-15 | NULL | 2004-12-19 | ACTIVE | 2 | 10 | 500.00 | 500.00 |
| 3 | CD | 1 | 2004-06-30 | NULL | 2004-06-30 | ACTIVE | 2 | 10 | 3000.00 | 3000.00 |
| 4 | CHK | 2 | 2001-03-12 | NULL | 2004-12-27 | ACTIVE | 2 | 10 | 2258.02 | 2258.02 |
| 5 | SAV | 2 | 2001-03-12 | NULL | 2004-12-11 | ACTIVE | 2 | 10 | 200.00 | 200.00 |
| 7 | CHK | 3 | 2002-11-23 | NULL | 2004-11-30 | ACTIVE | 3 | 13 | 1057.75 | 1057.75 |
| 8 | MM | 3 | 2002-12-15 | NULL | 2004-12-05 | ACTIVE | 3 | 13 | 2212.50 | 2212.50 |
| 10 | CHK | 4 | 2003-09-12 | NULL | 2005-01-03 | ACTIVE | 1 | 1 | 534.12 | 534.12 |
| 11 | SAV | 4 | 2000-01-15 | NULL | 2004-10-24 | ACTIVE | 1 | 1 | 767.77 | 767.77 |
| 12 | MM | 4 | 2004-09-30 | NULL | 2004-11-11 | ACTIVE | 1 | 1 | 5487.09 | 5487.09 |
| 13 | CHK | 5 | 2004-01-27 | NULL | 2005-01-05 | ACTIVE | 4 | 16 | 2237.97 | 2897.97 |
| 14 | CHK | 6 | 2002-08-24 | NULL | 2004-11-29 | ACTIVE | 1 | 1 | 122.37 | 122.37 |
| 15 | CD | 6 | 2004-12-28 | NULL | 2004-12-28 | ACTIVE | 1 | 1 | 10000.00 | 10000.00 |
| 17 | CD | 7 | 2004-01-12 | NULL | 2004-01-12 | ACTIVE | 2 | 10 | 5000.00 | 5000.00 |
| 18 | CHK | 8 | 2001-05-23 | NULL | 2005-01-03 | ACTIVE | 4 | 16 | 3487.19 | 3487.19 |
| 19 | SAV | 8 | 2001-05-23 | NULL | 2004-10-12 | ACTIVE | 4 | 16 | 387.99 | 387.99 |
| 21 | CHK | 9 | 2003-07-30 | NULL | 2004-12-15 | ACTIVE | 1 | 1 | 125.67 | 125.67 |
| 22 | MM | 9 | 2004-10-28 | NULL | 2004-10-28 | ACTIVE | 1 | 1 | 9345.55 | 9845.55 |
| 23 | CD | 9 | 2004-06-30 | NULL | 2004-06-30 | ACTIVE | 1 | 1 | 1500.00 | 1500.00 |
| 24 | CHK | 10 | 2002-09-30 | NULL | 2004-12-15 | ACTIVE | 4 | 16 | 23575.12 | 23575.12 |
| 25 | BUS | 10 | 2002-10-01 | NULL | 2004-08-28 | ACTIVE | 4 | 16 | 0.00 | 0.00 |
| 27 | BUS | 11 | 2004-03-22 | NULL | 2004-11-14 | ACTIVE | 2 | 10 | 9345.55 | 9345.55 |
| 28 | CHK | 12 | 2003-07-30 | NULL | 2004-12-15 | ACTIVE | 4 | 16 | 38552.05 | 38552.05 |
| 29 | SBL | 13 | 2004-02-22 | NULL | 2004-12-17 | ACTIVE | 3 | 13 | 50000.00 | 50000.00 |
+------------+------------+---------+------------+------------+--------------------+--------+----------------+-------------+---------------+-----------------+
分支表：
+-----------+---------------+----------------------+---------+-------+-------+
| branch_id | name | address | city | state | zip |
+-----------+---------------+----------------------+---------+-------+-------+
| 1 | Headquarters | 3882 Main St. | Waltham | MA | 02451 |
| 2 | Woburn Branch | 422 Maple St. | Woburn | MA | 01801 |
| 3 | Quincy Branch | 125 Presidential Way | Quincy | MA | 02169 |
| 4 | So. NH Branch | 378 Maynard Ln. | Salem | NH | 03079 |
+-----------+---------------+----------------------+---------+-------+-------+
员工表：
+--------+----------+-----------+------------+----------+-----------------+---------+--------------------+--------------------+
| emp_id | fname | lname | start_date | end_date | superior_emp_id | dept_id | title | assigned_branch_id |
+--------+----------+-----------+------------+----------+-----------------+---------+--------------------+--------------------+
| 1 | Michael | Smith | 2005-06-22 | NULL | NULL | 3 | President | 1 |
| 2 | Susan | Barker | 2006-09-12 | NULL | 1 | 3 | Vice President | 1 |
| 3 | Robert | Tyler | 2005-02-09 | NULL | 1 | 3 | Treasurer | 1 |
| 4 | Susan | Hawthorne | 2006-04-24 | NULL | 3 | 1 | Operations Manager | 1 |
| 5 | John | Gooding | 2007-11-14 | NULL | 4 | 2 | Loan Manager | 1 |
| 6 | Helen | Fleming | 2008-03-17 | NULL | 4 | 1 | Head Teller | 1 |
| 7 | Chris | Tucker | 2008-09-15 | NULL | 6 | 1 | Teller | 1 |
| 8 | Sarah | Parker | 2006-12-02 | NULL | 6 | 1 | Teller | 1 |
| 9 | Jane | Grossman | 2006-05-03 | NULL | 6 | 1 | Teller | 1 |
| 10 | Paula | Roberts | 2006-07-27 | NULL | 4 | 1 | Head Teller | 2 |
| 11 | Thomas | Ziegler | 2004-10-23 | NULL | 10 | 1 | Teller | 2 |
| 12 | Samantha | Jameson | 2007-01-08 | NULL | 10 | 1 | Teller | 2 |
| 13 | John | Blake | 2004-05-11 | NULL | 4 | 1 | Head Teller | 3 |
| 14 | Cindy | Mason | 2006-08-09 | NULL | 13 | 1 | Teller | 3 |
| 15 | Frank | Portman | 2007-04-01 | NULL | 13 | 1 | Teller | 3 |
| 16 | Theresa | Markham | 2005-03-15 | NULL | 4 | 1 | Head Teller | 4 |
| 17 | Beth | Fowler | 2006-06-29 | NULL | 16 | 1 | Teller | 4 |
| 18 | Rick | Tulman | 2006-12-12 | NULL | 16 | 1 | Teller | 4 |
+--------+----------+-----------+------------+----------+-----------------+---------+--------------------+--------------------+
最后一个选项并缩小选择标准的范围，以仅包括由出纳员或出纳员主管开立的账户。如果贷款经理或运营经理开立了该账户，则该账户将被排除在外。最后一个账户，并缩小了选择标准，仅包括由出纳员或出纳员主管开立的账户。如果贷款经理或运营经理开立了该账户，则该账户将被排除在外。中的“和”open\u emp\u id子句仅选择标题为“出纳员”或“出纳员负责人”的员工id。在您的情况下，结果并没有什么不同，因为您正在寻找名为“沃伯恩分行”的分行，而所有员工都只有“出纳员”或“出纳员负责人”的头衔，这只是巧合
| 10 | Paula | Roberts | 2006-07-27 | NULL | 4 | 1 | Head Teller | 2 |
| 11 | Thomas | Ziegler | 2004-10-23 | NULL | 10 | 1 | Teller | 2 |
| 12 | Samantha | Jameson | 2007-01-08 | NULL | 10 | 1 | Teller | 2 |
在第一个查询中将分支名称更改为“总部”，您将看到子查询产生的差异。“总部”中没有“出纳员”或“出纳员负责人”头衔的任何员工都将被排除在外。中的AND open\u emp\u id条款仅选择头衔为“出纳员”或“出纳员负责人”的员工id。在您的情况下，结果并没有什么不同，因为您正在寻找名为“沃伯恩分行”的分行，而所有员工都只有“出纳员”或“出纳员负责人”的头衔，这只是巧合
| 10 | Paula | Roberts | 2006-07-27 | NULL | 4 | 1 | Head Teller | 2 |
| 11 | Thomas | Ziegler | 2004-10-23 | NULL | 10 | 1 | Teller | 2 |
| 12 | Samantha | Jameson | 2007-01-08 | NULL | 10 | 1 | Teller | 2 |
在第一个查询中将分支名称更改为“总部”，您将看到子查询产生的差异。“总部”任何没有“出纳员”或“出纳员负责人”头衔的员工将被排除在外