TABLOCK(表锁) 此选项被选中时,SQL Server 将在整个表上置共享锁直至该命令结束。 这个选项保证其他进程只能读取而不能修改数据。 PAGLOCK(页锁) 此选项为默认选项, 当被选中时,SQL Server 使用共享页锁。 TABLOCKX(排它表锁) 此选项被选中时,SQL Server 将在整个表上置排它锁直至该命令或事务结束。这将防止...
|--Clustered Index Seek(OBJECT:([t1].[cidx]), SEEK:([t1].[c1]=[t1].[c1] AND [Uniq1002]=[Uniq1002]) LOOKUP ORDERED FORWARD) 我们看到了一个nested loops,第一行,利用索引t1.c2来进行seek,seek出来的那个rowid,在第二行中,用来通过聚集索引来查找整行的数据。这是什么?就是bookmark lookup啊!
(我正在使用 Microsoft SQL Server,2005) 一个简化的例子: SELECT col1, col2, col3, CASE WHEN condition THEN CASE WHEN condition1 THEN CASE WHEN condition2 THEN calculation1 ELSE calculation2 END ELSE CASE WHEN condition2 THEN calculation3 ELSE calculation4 END END ELSE CASE WHEN condition1 THEN...
SELECT c2, c3 FROM t1 WHERE c2 BETWEEN @p1 AND @p1+1 |--Nested Loops(Inner Join, OUTER REFERENCES:([Uniq1002], [t1].[c1])) |--Index Seek(OBJECT:([t1].[idx1]), SEEK:([t1].[c2] >= [@p1] AND [t1].[c2] <= [@p1]+(1)) ORDERED FORWARD) |--Clustered Index Seek(OBJEC...
在SQL Server中,SELECT语句用于从数据库中检索数据。CASE语句是SELECT语句中的一种条件表达式,用于根据条件返回不同的结果。 CASE语句有两种形式:简单CASE表达式和搜索CA...
selectcount(casewhen rn=1then task_idelsenullend)task_numfrom(select task_id,row_number()over(partition by task_id order by start_time)rn from Task)tmp; 此外,再借助一个表 test 来理理 distinct 和 group by 在去重中的使用: 代码语言:javascript ...
CASEmg.is_next_candidateWHEN1THEN'Yes'WHEN0THEN'No'ELSE'Memory has been granted'ENDAS'Next Candidate for Memory Grant', r.command ,ltrim(rtrim(replace(replace(substring(q.text,1,1000),char(10),' '),char(13),' '))) [text] , rs.target_memory_kb /1024ASserver_target_grant_memo...
Syntax for SQL Server, Azure SQL Database and Azure Synapse Analytics. syntaxsql -- Simple CASE expression:CASEinput_expressionWHENwhen_expressionTHENresult_expression[ ...n ] [ELSEelse_result_expression]END-- Searched CASE expression:CASEWHENBoolean_expressionTHENresult_expression[ ...n ] [ELSEels...
User-defined functions can be nested; that is, one user-defined function can call another. The nesting level is incremented when the called function starts execution, and decremented when the called function finishes execution. User-defined functions can be nested up to 32 levels. Exceeding the ...
Applies to: SQL Server 2016 (13.x) and later versions.Scope: Global or session. 715 Enables table lock for bulk load operations into a heap with no nonclustered indexes. When this trace flag is enabled, bulk load operations acquire bulk update (BU) locks when bulk copying data into a ...