id int primary key auto_increment, name char(16) )engine=innodb; 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. # auto_increment注意点: 1、通常与primary key连用,而且通常是给id字段加 2、auto_incremnt只能给被定义成key(unique key,primary key)的字段加 MySQL...
SELECT*,UUID()ASnew_uuidFROMyour_table; 1. 在这个查询语句中,SELECT *表示选择所有的列,UUID()是MySQL内置的函数,用来生成一个UUID。AS new_uuid表示将生成的UUID命名为new_uuid,并将其添加到结果列表中。 示例 假设我们有一个名为students的表,包含id、name和age三个字段。我们可以使用如下查询语句来在结果...
unique_subquery:用于where中的in查询,完全替换子查询,效率更高。语句为valueIN(SELECTprimary_keyFROMsingle_tableWHEREsome_expr)index_subquery:子查询中的返回结果字段组合是一个索引(或索引组合),但不是一个主键或唯一索引 range:索引范围查询,常见于使用=,<>,>,>=,<,<=,ISNULL,<=>,BETWEEN,IN()或者like...
"FILE_ID" is an int(11) value, and is indexed. Doing a "SELECT count(`FILE_ID`) FROM tableName" completes in under a second. The problem is that the "DISTINCT" query takes AGES to complete. I don't actually know how long, because I stopped the query after 25 minutes. Is there...
mysql> DROP INDEX foreign_id ON student; (3)、查看索引 SHOW {INDEX | INDEXES | KEYS} {FROM | IN} tbl_name mysql> SHOW INDEXES FROM student; 四、用户管理 (1)、创建用户 CREATE USER 'USERNAME'@'HOST' [IDENTIFIED BY 'PASSWORD']; mysql> CREATE USER 'admin'@'172.16.1.111' IDENTIFIED BY...
---表准备--- create table emp( id int not null unique auto_increment, name varchar(20) not null, sex enum('male','female') not null default 'male', #大部分是男的 age int(3) unsigned not null default 28, hire_date date not null, post varchar(50), post_comment varchar(100), ...
SELECT*FROMorder>1064-You have an errorinyourSQLsyntax;checkthe manual that correspondstoyour MySQL server versionfortherightsyntaxtousenear'order'at line1 正确的 代码语言:sql 复制 mysql>SELECT*FROM`ORDER`;+---+---+|order_id|order_name|+---+---+|1|shkstart||2|tomcat||3|dubbo|+---...
In MySQL 8.0, this behavior is changed. The current maximum auto-increment counter value is ...
unique index fulltext 索引覆盖 我们知道除了主键索引,其他的都是辅助索引,辅助索引检索会发生回表。 但有一种情况不会发生回表,那就是索引覆盖。 索引覆盖是指 查询的数据在索引中就取得了,即覆盖,那就不需要回表查询。 举个例子: select id,age from person where age=16; 从上图中可以看到,我们想要查询的...
Payments table has a unique "id", and a "cur_stat_id" which is what we are trying to populate with the most recent matching record from a related table (payment_status). INSERT INTO payments (id, cur_stat_id) SELECT id, x.statid FROM payments JOIN (SELECT payment_id, max(id) as...