MySQL 更新数据

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MySQL 更新数据

UPDATE 命令修改 MySQL 数据表数据的通用 SQL 语法：

UPDATE table_name SET field1=new-value1, field2=new-value2
[WHERE Clause]

你可以同时更新一个或多个字段。 你可以在 WHERE 子句中指定任何条件。 你可以在一个单独表中同时更新数据。

当你需要更新数据表中指定行的数据时 WHERE 子句是非常有用的。

https://www.runoob.com/mysql/mysql-update-query.html

[xgqfrms]

UPDATE Employees SET name = "Crew"
WHERE employee_id = 2;

UPDATE Employees SET employee_id=4,  name="Haven"
WHERE employee_id = 2;

UPDATE Employees SET employee_id=5,  name="Kristian"
WHERE employee_id = 3;

select * from Employees;

UPDATE Salaries SET salary=22517
WHERE employee_id = 1;

UPDATE Salaries SET employee_id=5,  salary=76071
WHERE employee_id = 2;

UPDATE Salaries SET employee_id=4,  salary=63539
WHERE employee_id = 3;

select * from Salaries;

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select * from Salaries;

select * from Employees;

SELECT *
FROM (
  SELECT employee_id FROM Employees
  UNION ALL
  SELECT employee_id FROM Salaries
) AS t;

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MySQL 数据库优化

https://www.imooc.com/video/3688