4 Answers. No, a view consists of a single SELECT statement. You cannot create or drop tables in a view. CTEs are temporary result sets that are defined within the execution scope of a single statement and they can be used in views.
This all means that temporary tables behave like any other sort of base table in that they are logged, and stored just like them. In practice, temporary tables are likely to remain cached in memory, but only if they are frequently-used: same as with a base table.
INSERT INTO SELECT statement reads data from one table and inserts it into an existing table. Such as, if we want to copy the Location table data into a temp table using the INSERT INTO SELECT statement, we have to specify the temporary table explicitly and then insert the data.
Where are the Temporary Tables stored? When we create a temporary table, they are created in the tempdb database. After creating a local temporary table, if we check the temporary tables folder in tempdb, we will see a weird table name.
The only difference between Union and Union All is that Union extracts the rows that are being specified in the query while Union All extracts all the rows including the duplicates (repeated values) from both the queries.
In a query editor, if you highlight the text of table name (ex dbo.MyTable) and hit ALT + F1 , you'll get a list of column names, type, length, etc.
Temporary Tables. A temporary table is a base table that is not stored in the database but instead exists only while the database session in which it was created is active. You must add data to a temporary table with SQL INSERT commands.
The DECLARE GLOBAL TEMPORARY TABLE statement defines a temporary table for the current connection. These tables do not reside in the system catalogs and are not persistent. Temporary tables exist only during the connection that declared them and cannot be referenced outside of that connection.
A temporary table exist solely for storing data within a session. The best time to use temporary tables are when you need to store information within SQL server for use over a number of SQL transactions. If you create a temporary table in one session and log out, it will not be there when you log back in.
You can create and use temporary tables in a stored procedure, but the temporary table exists only for the duration of the stored procedure that creates it. A single procedure can: Create a temporary table. Insert, update, or delete data.
We can also use the following query to display all Oracle global temporary tables: select table_name from all_tables where temporary = 'Y';
Local SQL Server temp tables are created using the pound symbol or “hashtag†followed by the table name. For example: #Table_name. SQL temp tables are created in the tempdb database. A local SQL Server temp table is only visible to the current session.
Temporary Tables are physically created in the tempdb database. Table Variable acts like a variable and exists for a particular batch of query execution. It gets dropped once it comes out of batch. It is created in the memory database but may be pushed out to tempdb.
Script to create Global Temporary table, using stored procedure is given below.
- Create Procedure Sp_GlobalTempTable.
- as.
- Begin.
- Create Table ##MyDetails(Id int, Name nvarchar(20))
- Insert into ##MyDetails Values(1, 'SATYA1')
- Insert into ##MyDetails Values(2, 'SATYA2')
- Insert into ##MyDetails Values(3, 'SATYA3')
Temporary tables are automatically dropped when they go out of scope, unless explicitly dropped by using DROP TABLE: A local temporary table created in a stored procedure is dropped automatically when the stored procedure is finished.
Even if you can't remove a temporary table, you may be able to drastically improve performance by making sure that the code that populates the temporary table is correctly filtering the data pulled from source tables.
Using the DROP TABLE command on a temporary table, as with any table, will delete the table and remove all data. In an SQL server, when you create a temporary table, you need to use the # in front of the name of the table when dropping it, as this indicates the temporary table.
This biggest difference is that a CTE can only be used in the current query scope whereas a temporary table or table variable can exist for the entire duration of the session allowing you to perform many different DML operations against them.
If you want to update a table (actual table, table variable or temporary table) with values from one or more other tables, then you must JOIN the tables.
The reason, temp tables are faster in loading data as they are created in the tempdb and the logging works very differently for temp tables. All the data modifications are not logged in the log file the way they are logged in the regular table, hence the operation with the Temp tables are faster.
A temp table can have indexes, whereas a table variable can only have a primary index. If speed is an issue Table variables can be faster, but obviously if there are a lot of records, or the need to search the temp table of a clustered index, then a Temp Table would be better.
