temp-tables

问题 Which are more performant, CTE or Temporary Tables ? 回答1: I'd say they are different concepts but not too different to say "chalk and cheese". A temp table is good for re-use or to perform multiple processing passes on a set of data. A CTE can be used either to recurse or to simply improved readability. And, like a view or inline table valued function can also be treated like a macro to be expanded in the main query A temp table is another table with some rules around scope I have stored

问题 Is it possible to create a temporary (session only) table from a select statement without using a create table statement and specifying each column type? I know derived tables are capable of this, but those are super-temporary (statement-only) and I want to re-use. It would save time if I did not have to write up a create table command and keep the column list and type list matched up. 回答1: CREATE TEMPORARY TABLE IF NOT EXISTS table2 AS (SELECT * FROM table1) From the manual found at http:/

问题 I\'m learning more details in table variable. It says that temp tables are always on disk, and table variables are in memory, that is to say, the performance of table variable is better than temp table because table variable uses less IO operations than temp table. But sometimes, if there are too many records in a table variable that can not be contained in memory, the table variable will be put on disk like the temp table. But I don\'t know what the \"too many records\" is. 100,000 records?

问题 What is the difference between local and global temporary tables in SQL Server? 回答1: I find this explanation quite clear (it's pure copy from Technet): There are two types of temporary tables: local and global. Local temporary tables are visible only to their creators during the same connection to an instance of SQL Server as when the tables were first created or referenced. Local temporary tables are deleted after the user disconnects from the instance of SQL Server. Global temporary tables

问题 In SQL Server 2005, we can create temp tables one of two ways: declare @tmp table (Col1 int, Col2 int); or create table #tmp (Col1 int, Col2 int); What are the differences between these two? I have read conflicting opinions on whether @tmp still uses tempdb, or if everything happens in memory. In which scenarios does one out-perform the other? 回答1: There are a few differences between Temporary Tables (#tmp) and Table Variables (@tmp), although using tempdb isn't one of them, as spelt out in

问题 My database contains three tables called Object_Table , Data_Table and Link_Table . The link table just contains two columns, the identity of an object record and an identity of a data record. I want to copy the data from DATA_TABLE where it is linked to one given object identity and insert corresponding records into Data_Table and Link_Table for a different given object identity. I can do this by selecting into a table variable and the looping through doing two inserts for each iteration. Is