MyBatis提供了@One注解来使用嵌套select语句(Nested-Select)加载一对一关联查询数据。让我们看看怎样使用@One注解获取学生及其地址信息。 public interface StudentMapper { @Select("SELECT ADDR_ID AS ADDRID, STREET, CITY, STATE, ZIP, COUNTRY FROM ADDRESSES WHERE ADDR_ID=#{id}") Address findAddress...
STATEMENT STACK的定义 STATEMENT STACK 是events_statements_current表被后用于存储当前会话执行语句堆栈的数据结构。... */ uint statement_stack_max; /** nested statement lost */ uint nested_statement_lost; struct PFS_ALIGNED...nested_statement_lost 存储丢失的语句数量 STATEMENT STACK相关小实验 1) 创建...
ID OPERATION OPTIONS OBJECT_NAME OPT COST--- --- --- --- --- ---0 SELECT STATEMENT CHO1 NESTED LOOPS 1252 VIEW 1163 SORT UNIQUE 1164 TABLE ACCESS FULL ORDERS ANA 405 TABLE ACCESS BY INDEX ROWID EMPLOYEES ANA 16 INDEX UNIQUE SCAN EMP_EMP_ID_PK ANA The following SQL statement usesEX...
SQL_CU_DML_STATEMENTS = 所有数据操作语言语句都支持目录:SELECT、INSERT、UPDATE、DELETE;如果受支持,则SELECT FOR UPDATE 和定位更新和删除语句。SQL_CU_PROCEDURE_INVOCATION = ODBC 过程调用语句支持目录。SQL_CU_TABLE_DEFINITION = 所有表定义语句都支持目录:CREATE TABLE、CREATE VIEW、ALTER TABLE、DROP TABLE ...
一、优化SELECT语句 这里只列出了最常见的优化,更多的优化内容请参考官方文档:Optimizing SELECT Statements 1.where子句优化 官方文档:WHERE Clause Optimization 这里总结where语句的优化,以select为例,但同样适用于update和delete语句。 2.Range Optimization(范围优化) ...
EXEC sp_create_plan_guide @name = N'Guide1', @stmt = N'SELECTc.LastName, c.FirstName, e.TitleFROMHumanResources.EmployeeASeJOINPerson.ContactAScONe.ContactID = c.ContactIDWHEREe.ManagerID =2;', @type = N'SQL', @module_or_batch = NULL, @params = NULL, @hints = N'OPTION (TABLE...
SQL92_SECURITY lets you specify whether users must have been granted the SELECT object privilege in order to execute such UPDATE or DELETE statements. SQL_TRACE Parameter type Boolean Default value false Parameter class Static Range of values true | false The value of SQL_TRACE ...
OrderedQueryOrExpr 方法的定义如下,该方法主要用于处理行表达式以及包含可选ORDER BY的 SELECT 语句。从方法实现逻辑可以看出,它首先调用 QueryOrExpr 方法构造了 SqlSelect 对象,然后再调用 OrderByLimitOpt 方法包装成 SqlOrderBy 对象。 /*** Parses either a row expression or a query expression with an opt...
A single statement with nested subqueries needs to be rewritten, or a complex script must be split into multiple statements. Data from different data sources are prepared at different time points, and the time gap is large. For example, the data from one data source is prepared at 01:00, ...
Problem description: For Oracle database 11g, the SQL statement runs normally if it only contains the SELECT statement, and an error occurs when theSUBSTR()function is added after the SELECT statement, indicating "OALL8 is in an inconsistent state". Both SQL statements can be successfully execute...