Temporary Tables And Table Variables In SQL 基本常识 1. 局部临时表(#开头)只对当前连接有效,当前连接断开时自动删除 2. 全局临时表(##开头)对其它连接也有效,在当前连接和其他访问过它的连接都断开时自动删除 3. 临时表就像普通表一样,它可以做索引等等 4. 临时表存在 tempdb database, 表变量存在 memory...
Temporary Table vs Table Variable There are two ways to create a temporary table: 1. ‘On the fly’ by designating an “INTO” clause after a SELECT statement and before a FROM clause: 2. The same way as defining an actual table by using the following syntax: ...
Temporary Tables And Table Variables In SQL 基本常识 1. 局部临时表(#开头)只对当前连接有效,当前连接断开时自动删除 2. 全局临时表(##开头)对其它连接也有效,在当前连接和其他访问过它的连接都断开时自动删除 3. 临时表就像普通表一样,它可以做索引等等 4. 临时表存在 tempdb database, 表变量存在 memory...
根据我查到的官方资料,说的是在SQL Server 2000下: “A table variable is not a memory-only structure. Because a table variable might hold more data than can fit in memory, it has to have a place on disk to store data. Table variables are created in the tempdb database similar to tempor...
In SQL Server, the concurrent creation of temporary tables from many sessions can lead to tempdb metadata contention. Tempdb metadata contention does not affect the concurrent creation of table variables. When SQL Server creates temporary tables, it has to update metadata inform...
由于表变量定义完毕以后,不支持对表变量结构的任何变更和索引创建,所以很多人会认为表变量不能创建索引,比如这篇文章SQL Server Temp Table vs Table Variable Performance Testing中的这句话“However, when we query rows using the indexed column of the temporary table, which is not indexed in the table ...
在研究临时表和表变量该如何选择的时候,一篇文章叫着SQL Server Temp Table vs Table Variable Performance Testing文章引用率是非常高的。通读全文,作者褒“临时表”贬“表变量”的语调跃然纸上,虽然原作者也有唯物辩证的思维去看待这个问题。但,综合起来原作者认为临时表性能好于表变量。事实上真的是这样子的吗?这...
After declaring our temporary table #T and our table-variable @T, we assign each one with the same "old value" string. Then, we begin a transaction that updates their contents. At this point, both will now contain the same "new value" string. But when we rollback the transaction, as...
However, once the dynamic SQL is run, there would be no table variable There are a few anomalies to be aware of too. You can’t, for example, change the table definition after the initial DECLARE statement. In SQL Server 2000, a table variable can’t be the destination of a SELECT ...
table variables provide the following benefits over temporary tables for small-scale queries that have query plans that don't change and when recompilation concerns are dominant: A table variable behaves like a local variable. It has a well-defined scope. This variable can be used in the functi...