From 1069128f0e3b8df5a520e075483404585133913c Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?=E7=8E=8B=E4=BC=8D=E6=B4=8B?= <593506802@qq.com> Date: Fri, 19 Jun 2020 20:19:33 +0800 Subject: [PATCH] update 2003/DBA1_DAY02. --- 2003/DBA1_DAY02 | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/2003/DBA1_DAY02 b/2003/DBA1_DAY02 index 66b0570..a03e4c3 100644 --- a/2003/DBA1_DAY02 +++ b/2003/DBA1_DAY02 @@ -16,7 +16,7 @@ mysql> insert into db1.t13(class) values ("nsd2003"); mysql> insert into db1.t13 values ("nsd2004" , "john" , 28); mysql> insert into db1.t13 values ( null, "null" , 27 ); mysql> select * from db1.t13; - 练习一下 到 14：45 + mysql> insert into db1.t13 values ( null, null , null ); ERROR 1048 (23000): Column 'name' cannot be null mysql> @@ -44,14 +44,14 @@ mysql> alter table t1 add class char(7) first; mysql> alter table t1 add tel char(11) not null default "010" ; mysql> alter table t1 add qq varchar(11) after name , add sex enum("man","woman") default "man" after email; mysql> desc db1.t1; - 5分钟 到15：50 + modify 修改字段类型 (注意：修改的新数据类型和约束条件不能与已经存储的数据矛盾) mysql> alter table t1 modify tel varchar(10) not null default "120"; mysql> alter table t1 modify tel varchar(10) not null default "120" after name; mysql> desc t1; - 练习到 16：36 + change 修改字段名 （同时也修改字段的类型） mysql> alter table t1 change email youxiang char(30) not null default "stu@tedu.cn" ; mysql> alter table t1 change class banji char(7) ; @@ -73,7 +73,7 @@ mysql> show tables; 索引的优缺点？ 加快查询数据的速度 减慢写的速度，同时占用物理存储空间 - 休息得到17：20 + 新华字典 目 录 1-200页 笔画排序 @@ -114,7 +114,7 @@ mysql> create table t22 ( mysql> insert into t21 values ("bob","nsd2003",null); ERROR 1048 (23000): Column 'stu_num' cannot be null mysql> -mysql> insert into t21 values ("bob","nsd2003","nsd200301"); 10:40上课 +mysql> insert into t21 values ("bob","nsd2003","nsd200301"); Query OK, 1 row affected (0.00 sec) mysql> insert into t21 values ("tom","nsd2003","nsd200301"); -- Gitee