mysql基礎語句

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++mysql 基礎操作
//主鍵549830479
alter table tabelname add new_field_id int(5) unsigned default 0 not null auto_increment ,add primary key (new_field_id);
//增加一個新列549830479
alter table t2 add d timestamp;
alter table infos add ex tinyint not null default '0';
//刪除列549830479
alter table t2 drop column c;
//重命名列549830479
alter table t1 change a b integer;
//改變列的類型549830479
alter table t1 change b b bigint not null;
alter table infos change list list tinyint not null default '0';
//重命名錶549830479
alter table t1 rename t2;
加索引549830479
mysql> alter table tablename change depno depno int(5) not null;
mysql> alter table tablename add index 索引名 (字段名1[，字段名2 …]);
mysql> alter table tablename add index emp_name (name);
加主關鍵字的索引549830479
mysql> alter table tablename add primary key(id);
加唯一限制條件的索引549830479
mysql> alter table tablename add unique emp_name2(cardnumber);
刪除某個索引549830479
mysql>alter table tablename drop index emp_name;
修改表：549830479
增加字段：549830479
mysql> ALTER TABLE table_name ADD field_name field_type;
修改原字段名稱及類型：549830479
mysql> ALTER TABLE table_name CHANGE old_field_name new_field_name field_type;
刪除字段：549830479
mysql> ALTER TABLE table_name DROP field_name;

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++mysql 約束
--------添加主鍵約束(bookid作爲主鍵)
alter table bookmessage
add constraint pk_bookid primary key(bookid)
--------添加唯一約束
alter table bookmessage
add constraint uq_bookid UNIQUE(bookid)
---------添加默認約束
alter table bookmessage
add constraint df_address DEFAUIT('地址不詳') for Address
--------添加檢出約束,要求年齡只能在15---40之間
alter table readermessage
add constraint CK_age CHECK(age BETWEEN 15 AND 40)
-------添加外鍵約束
alter table bookmessage
add constraint fk_bookid
foreign key(bookid)<外鍵> references readermessage<表>(readerid)<表中的主鍵>
-------刪除約束
alter table 表名
drop constraint 約束名
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