事务控制语句(Transaction Control Statement)用于实现数据库事务管理 COMMIT、ROLLBACK、SAVEPOINT 5、会话控制语句 会话控制语句(Session Control Statement)用于动态修改当前用户会话的属性,在应用开发层面极少用到。 ALTER SESSION、SET ROLE 二、SQL基础 1、删除表中数据 使用DELET指令,可删除数据表中已有的数据,例如: ...
The following illustrates the syntax of the OracleMERGEstatement: MERGEINTOtarget_tableUSINGsource_tableONsearch_conditionWHENMATCHEDTHENUPDATESETcol1 = value1, col2 = value2,...WHERE<update_condition> [DELETEWHERE<delete_condition>]WHENNOTMATCHEDTHENINSERT(col1,col2,...)values(value1,value2,.....
Syntax:AUTO_REOPTIMIZE Description:The AUTO_REOPTIMIZE hint instructs the optimizer to automatically change a plan on subsequent executions of a SQL statement. Note: The "automatic reoptimization" is the ability of the optimizer to automatically change a plan on subsequent executions of a SQL sta...
When using the merge statement, remember that you can have all three primary DML statements, insert, update and delete. One table as the source where new or updated rows are provided along with the relevant columns, or, you can have deleted rows too by specifying another column as the indic...
数据操纵语言,Data manipulation language,检称DML,主要包括检索(SELECT)、插入(INSERT)、更新(UPDATE)、删除(DELETE),是SQL的一个核心部分。一条DML将开始一个事务,接下来的DML都是同一事务中的语句,直到提交(COMMIT)或回滚(ROLLBACK)。下面我们来逐一介绍下ORACLE中的插入、更新、删除和合并(MERGE)的语法及实例解析...
merge into是特有的功能,相当于在 MSSQL中的 ifexists(...) updatetable else Insertinto table. mergeinto语法不仅没有if exists语法啰嗦,而且比if exists还要高效很多,常用来在oracle之间同步数据库表。 例子: 1、创建测试表及数据 [c-sharp] ...
SQL>The output shows the straight MERGE statement is an order of magnitude faster than its nearest rival. The update/insert performs almost twice the speed of the insert/update and even out performs the row-by-row MERGE.Just comparing the update/insert and the insert/update methods in ...
Merge用于需要使用SQL语句同时进行Insert/Update的操作,也就是说当存在记录时就更新(Update),不存在数据时就插入(Insert)。 执行Merge前: 执行以下语句: Merge Into products t Using newproducts s On (t.product_id=s.product_id) When Matched Then Update Set t.product_name=s.product_name,t.Category=s...
Merge语句可以用来插入或更新数据,取决于数据是否已经存在。 语法结构: MERGE INTO table_name --目标表,待更新 USING table_name --源表/视图 ON (condition) --条件语句,若为真,则记录更新;若为假,则记录插入 WHEN MATCHED THEN update_clause --条件为真时,执行语句 ...
merge into sales_history sh using sales s on (s.prod=sh.prod and s.month=sh.month) when matched then update set sh.amount=s.amount when not matched then insert values (prod,month,amount); After the statement is executed sales_history table will look like this....