使用其中一种相对于另一种有哪些优势:
DATEPART(YEAR, GETDATE())
相对于:
YEAR(GETDATE())
有性能差异吗?如果是的话,哪一个最快?
最佳答案
没有什么区别。在执行计划中,两者都被翻译为datepart(year,getdate())
。
对于 SQL Server 2005、2008 和 2012 来说都是如此。
select datepart(year, getdate())
from (select 1 x) x
select year(getdate())
from (select 1 x) x
执行计划。
<?xml version="1.0" encoding="utf-16"?>
<ShowPlanXML xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" Version="1.0" Build="9.00.5057.00" xmlns="http://schemas.microsoft.com/sqlserver/2004/07/showplan">
<BatchSequence>
<Batch>
<Statements>
<StmtSimple StatementCompId="1" StatementEstRows="1" StatementId="1" StatementOptmLevel="TRIVIAL" StatementSubTreeCost="1.157E-06" StatementText="select datepart(year, getdate())
from (select 1 x) x

" StatementType="SELECT">
<StatementSetOptions ANSI_NULLS="false" ANSI_PADDING="false" ANSI_WARNINGS="false" ARITHABORT="true" CONCAT_NULL_YIELDS_NULL="false" NUMERIC_ROUNDABORT="false" QUOTED_IDENTIFIER="false" />
<QueryPlan DegreeOfParallelism="0" CachedPlanSize="8" CompileTime="23" CompileCPU="23" CompileMemory="64">
<RelOp AvgRowSize="11" EstimateCPU="1.157E-06" EstimateIO="0" EstimateRebinds="0" EstimateRewinds="0" EstimateRows="1" LogicalOp="Constant Scan" NodeId="0" Parallel="false" PhysicalOp="Constant Scan" EstimatedTotalSubtreeCost="1.157E-06">
<OutputList>
<ColumnReference Column="Expr1001" />
</OutputList>
<RunTimeInformation>
<RunTimeCountersPerThread Thread="0" ActualRows="1" ActualEndOfScans="1" ActualExecutions="1" />
</RunTimeInformation>
<ConstantScan>
<Values>
<Row>
<ScalarOperator ScalarString="datepart(year,getdate())">
<Identifier>
<ColumnReference Column="ConstExpr1002">
<ScalarOperator>
<Intrinsic FunctionName="datepart">
<ScalarOperator>
<Const ConstValue="(0)" />
</ScalarOperator>
<ScalarOperator>
<Intrinsic FunctionName="getdate" />
</ScalarOperator>
</Intrinsic>
</ScalarOperator>
</ColumnReference>
</Identifier>
</ScalarOperator>
</Row>
</Values>
</ConstantScan>
</RelOp>
</QueryPlan>
</StmtSimple>
</Statements>
</Batch>
<Batch>
<Statements>
<StmtSimple StatementCompId="2" StatementEstRows="1" StatementId="2" StatementOptmLevel="TRIVIAL" StatementSubTreeCost="1.157E-06" StatementText="select year(getdate())
from (select 1 x) x" StatementType="SELECT">
<StatementSetOptions ANSI_NULLS="false" ANSI_PADDING="false" ANSI_WARNINGS="false" ARITHABORT="true" CONCAT_NULL_YIELDS_NULL="false" NUMERIC_ROUNDABORT="false" QUOTED_IDENTIFIER="false" />
<QueryPlan DegreeOfParallelism="0" CachedPlanSize="8" CompileTime="0" CompileCPU="0" CompileMemory="64">
<RelOp AvgRowSize="11" EstimateCPU="1.157E-06" EstimateIO="0" EstimateRebinds="0" EstimateRewinds="0" EstimateRows="1" LogicalOp="Constant Scan" NodeId="0" Parallel="false" PhysicalOp="Constant Scan" EstimatedTotalSubtreeCost="1.157E-06">
<OutputList>
<ColumnReference Column="Expr1001" />
</OutputList>
<RunTimeInformation>
<RunTimeCountersPerThread Thread="0" ActualRows="1" ActualEndOfScans="1" ActualExecutions="1" />
</RunTimeInformation>
<ConstantScan>
<Values>
<Row>
<ScalarOperator ScalarString="datepart(year,getdate())">
<Identifier>
<ColumnReference Column="ConstExpr1002">
<ScalarOperator>
<Intrinsic FunctionName="datepart">
<ScalarOperator>
<Const ConstValue="(0)" />
</ScalarOperator>
<ScalarOperator>
<Intrinsic FunctionName="getdate" />
</ScalarOperator>
</Intrinsic>
</ScalarOperator>
</ColumnReference>
</Identifier>
</ScalarOperator>
</Row>
</Values>
</ConstantScan>
</RelOp>
</QueryPlan>
</StmtSimple>
</Statements>
</Batch>
</BatchSequence>
</ShowPlanXML>
关于sql-server - 日期部分(年份,...)与年份(...),我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/14850239/