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MySQL24

作者:互联网

更新记录

更新记录通过UPDATE语句实现,其(单表更新)语法为:

UPDATE TABLE  SET col_name={expr|DEFAULT} [ ,… ] [ WHERE WHERE_cONditiON ]

说明:
UPDATE语句更新记录,并且返回被更新的行数(记录数);
SET子句指明被更新的列及其列值,列值可以是表达式或者默认值(用DEFAULT表示);
对于声明为NOT NULL的列在尝试更新为NULL时,在严格的SQL模式下将产生错误;
如果省略WHERE子句,则更新全部记录;

CREATE TABLE employee( 
    id SMALLINT UNSIGNED KEY AUTO_INCREMENT, 
    employee_name VARCHAR(20) NOT NULL, 
    bASe_pay DECIMAL(7,2) UNSIGNED NOT NULL DEFAULT 0, 
    bONus   DECIMAL(7,2) UNSIGNED NOT NULL DEFAULT 0, 
    taxes   DECIMAL(7,2) UNSIGNED NOT NULL DEFAULT 0, 
    deserve DECIMAL(7,2) UNSIGNED NOT NULL DEFAULT 0 
);   
INSERT employee(employee_name,bASe_pay,bONus,taxes) VALUES('王志强',36200,5000,200.85); 
INSERT employee(employee_name,bASe_pay,bONus,taxes) VALUES('张宇宁',32000,4000,160.01); 
INSERT employee(employee_name,bASe_pay,bONus,taxes) VALUES('刘昌涛',29000,7800,310.50); 
INSERT employee(employee_name,bASe_pay,bONus,taxes) VALUES('纪盈新',41009.35,600,315.36); 
INSERT employee(employee_name,bASe_pay,bONus,taxes) VALUES('肖莉娟',50000,5000,795.33);  
UPDATE employee SET deserve = bASe_pay + bONus - taxes; 

标签:bONus,pay,taxes,bASe,employee,NULL,MySQL24
来源: https://www.cnblogs.com/sean-test/p/15451490.html