43.将所有to_date为9999-01-01的全部更新为NULL.md · jiefyxx/数据库SQL实战

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43.将所有to_date为9999-01-01的全部更新为NULL.md 954 Bytes

authored 2019-08-13 08:38 . revise:content revision

# 将所有to_date为9999-01-01的全部更新为NULL

## 题目描述

将所有to_date为9999-01-01的全部更新为NULL,且 from_date更新为2001-01-01。

```mysql
CREATE TABLE IF NOT EXISTS titles_test (
id int(11) not null primary key,
emp_no int(11) NOT NULL,
title varchar(50) NOT NULL,
from_date date NOT NULL,
to_date date DEFAULT NULL);

insert into titles_test values ('1', '10001', 'Senior Engineer', '1986-06-26', '9999-01-01'),
('2', '10002', 'Staff', '1996-08-03', '9999-01-01'),
('3', '10003', 'Senior Engineer', '1995-12-03', '9999-01-01'),
('4', '10004', 'Senior Engineer', '1995-12-03', '9999-01-01'),
('5', '10001', 'Senior Engineer', '1986-06-26', '9999-01-01'),
('6', '10002', 'Staff', '1996-08-03', '9999-01-01'),
('7', '10003', 'Senior Engineer', '1995-12-03', '9999-01-01');
```

## 答案

```mysql
update titles_test set to_date = null , from_date = '2001-01-01' where to_date = '9999-01-01';
```

## 题解

update的使用

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