SQL Server中基于函数的索引 [英] Function-based indexes in SQL Server
问题描述
在PostgreSQL中,我可以创建一个基于函数的索引,而不是在Oracle或PostgreSQL中存在类似于Oracle或PostgreSQL的基于索引的索引使用以下语法使用:
CREATE INDEX sample ONTestDB((expression1||''||表达式2\" ));
我发现了一个文章,在SQL Server中我发现了一些名为计算列上的索引的东西。这是一个基于函数的索引,就像在Oracle / PostgreSQL中一样?任何人都可以提供一个示例查询来创建/查看这样的索引?
我根据Damien的评论进一步研究了发现一个答案非常接近于匹配Oracle / PostgreSQL基于函数的索引。
我有一个名为 PARCELS
在那里我通过使用以下给出的alter语句创建了一个新列 COMPUTEDPARCELS
:
ALTER TABLE [PARCELS] ADD COMPUTEDPARCELS AS CONVERT(CHAR(8),[MAPNO],112);
然后在计算列上创建一个索引:
CREATE INDEX function_index ON [PARCELS](COMPUTEDPARCELS);
当然,这个例子很简单,但行为就像一个基于函数的索引。
I'm trying to understand if function based indexes similar to the one's in Oracle or PostgreSQL exist in SQL Server
In PostgreSQL, I can create a function based index using by using the following syntax:
CREATE INDEX sample ON "TestDB" (("expression1" || ' ' || "expression2"));
I found a article where I found something called "index on computed columns" in SQL Server. Is this a function based index just like in Oracle/PostgreSQL? Can anybody provide me a sample query to create/view such an index?
I researched a bit further based on Damien's comment and found an answer that comes very close to matching Oracle's/PostgreSQL's function based indexes.
I have a table named PARCELS
where I created a new column COMPUTEDPARCELS
by using the alter statement as given below:
ALTER TABLE [PARCELS] ADD COMPUTEDPARCELS AS CONVERT(CHAR(8), [MAPNO], 112);
And then create an index on the computed column:
CREATE INDEX function_index ON [PARCELS](COMPUTEDPARCELS);
Of course the example is pretty simple but behaves just like a function based index.
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