select * from info limit 5; -- 获取前5条数据 select * from info order by id desc limit 3; -- 先排序,再获取前3条数据 select * from info where id > 4 order by id desc limit 3; -- 先取符合条件的数据,再排序,最后获取前3条数据 select * from info limit 3 offset 2; -- 从索引2...
mybatis select查询使用返回结果为resultMap <select id="findPageObjects" resultMap="sysUserMap"> select * from sys_users where id = #{id} order by createTime desc limit #{startIndex},#{pageSize} </select> <resultMap type="com.demo.vo.SysUserDeptResult" id="sysUserMap"> <!--说明:对于...
| GRANT BACKUP_ADMIN,BINLOG_ADMIN,CONNECTION_ADMIN,ENCRYPTION_KEY_ADMIN,GROUP_REPLICATION_ADMIN,PERSIST_RO_VARIABLES_ADMIN,REPLICATION_SLAVE_ADMIN,RESOURCE_GROUP_ADMIN,RESOURCE_GROUP_USER,ROLE_ADMIN,SET_USER_ID,SYSTEM_VARIABLES_ADMIN,XA_RECOVER_ADMIN ON *.* TO `root`@`localhost` WITH GRANT OPTION...
),也就是select dname from dept d where e.deptno = d.deptno但是这部分是不能单独执行的,所以猜测mysql对这部分做了处理,处理成类似这种select...= 3; Subquery returns more than 1 row 子查询中的limit mysql> select d.dname,(select e.ename from emp e where...子查询中除了使用limit还可以...
批发价在300-400之间的货品SELECTid productName,salePriceFROMproductWHEREsalePrice>=300ANDsalePrice<=400需求: 选择id,货品名称,分类编号为2,4的所有货品SELECTid productName,salePriceFROMproductWHEREdir_id=3ORdir_id<=4需求: 选择id,货品名词,分类编号不为2的所有商品SELECTid productName,salePriceFROM...
...查看正在等待锁资源的查询 select * from performance_schema.data_lock_waits; select * from sys.innodb_lock_waits;...查看锁定数据 select * from performance_schema.data_locks; 查看正在运行中的事务或命令的详情 select * from information_schema.innodb_trx...避免全表锁的关键在于优化查询,利用索引...
sys_connect_by_path(col, separtor): returns the connection path from the root node to the current row. Thecolparameter indicates the name of the column displayed in the path, and theseparatorparameter indicates the connector. connect_by_root(col): displays the top-level node of the node.co...
使用 RESERVED_KEYWORDS 选项可启用 LIMIT 关键字。 注意 不能在同一查询中指定 TOP 和 LIMIT。 示例 (返回顶部) 示例1 列出系统目录中的所有表和视图: SELECT tname FROM SYS.SYSCATALOG WHERE tname LIKE 'SYS%' ; 示例2 列出所有客户及其订单总值: SELECT CompanyName, CAST( sum(SalesOrderItems.Quantity ...
select segment_name,status from dba_rollback_segs; 说明:输出结果中所有回滚段的“STATUS”应该为“ONLINE”。 2、数据库相关资源使用情况检查 (1)检查Oracle初始化文件中相关参数值 select resource_name,max_utilization,initial_allocation, limit_value from v$resource_limit; ...
CREATE TABLE ... SELECTalways performs an implicit commit (Section 15.3.3, “Statements That Cause an Implicit Commit”). If the destination table does not exist, logging occurs as follows. It does not matter whetherIF NOT EXISTSis present. ...