What is a drop table?
The drop table command is used to delete a table and all rows in the table. ... Deleting all of the records in the table leaves the table including column and constraint information. Dropping the table removes the table definition as well as all of its rows.
What happens when you drop a table in SQL?
We use the SQL DROP Table command to drop a table from the database. It completely removes the table structure and associated indexes, statistics, permissions, triggers and constraints. You might have SQL Views and Stored procedures referencing to the SQL table.
What is drop table if exists?
The DROP TABLE statement deletes the specified table, and any data associated with it, from the database. The IF EXISTS clause allows the statement to succeed even if the specified tables does not exist. ... Attempting to drop the table before dropping the procedure will result in an error.
Are indexes dropped when a table is dropped?
DROP TABLE always removes - 1. any indexes 2. ... constraints that exist for the target table.
Are temp tables dropped automatically?
Local temp tables (single # in the name) will be automatically dropped when out of scope, hence explicit dropping makes no sense if the scope is short lived (a stored procedure for example).
Should I drop temp table at end of stored procedure?
If you're done with a temporary table and you have a lot more other processing to do, drop it. If you use a temporary table right to the end of a procedure, leave it there. It'll get cleaned up in due course. Your drop isn't going to affect things in that case.
Do you need to drop temp table in stored procedure?
If you are wondering why it is not required to drop the temp table at the end of the stored procedure, well, it is because when the stored procedure completes execution, it automatically drops the temp table when the connection/session is dropped which was executing it.
How do I know if a temp table exists?
Again, the best sure-fire way to do it is to just check for OBJECT_ID('TEMPDB.. #TEST')... if it's NOT NULL, then the temp table exists.
How do you drop a table if it exists in SQL?
SQL Server DROP TABLE
- First, specify the name of the table to be removed.
- Second, specify the name of the database in which the table was created and the name of the schema to which the table belongs. The database name is optional. ...
- Third, use IF EXISTS clause to remove the table only if it exists.
How do you drop a table variable in SQL?
We cannot drop a table variable using an explicit drop statement. It is stored in the tempdb system database. The storage for the table variable is also in the tempdb database. We can use temporary tables in explicit transactions as well....We use the following format for defining a temporary table:
What is a temporary table in SQL?
A temporary table in SQL Server, as the name suggests, is a database table that exists temporarily on the database server. A temporary table stores a subset of data from a normal table for a certain period of time. ... Temporary tables are stored inside “tempdb” which is a system database.
Are temp tables faster than CTE?
If you are joining multiple tables with millions of rows of records in each, CTE will perform significantly worse than temporary tables. Temp tables are always on disk - so as long as your CTE can be held in memory, it would most likely be faster (like a table variable, too).
What is magic table in SQL?
There are Magic Tables (virtual tables) in SQL Server that hold the temporal information of recently inserted and recently deleted data in the virtual table. ... A magic table can be utilized in INSERT, UPDATE, and DELETE activity with the table in a trigger, which is the common understanding of people.
Is CTE a temp table?
Temp Tables are physically created in the tempdb database. These tables act as the normal table and also can have constraints, an index like normal tables. CTE is a named temporary result set which is used to manipulate the complex sub-queries data. ... This is created in memory rather than the Tempdb database.
Are CTEs faster than subqueries?
The performance of CTEs and subqueries should, in theory, be the same since both provide the same information to the query optimizer. One difference is that a CTE used more than once could be easily identified and calculated once. The results could then be stored and read multiple times.
Can you index a CTE?
A CTE is a temporary, "inline" view - you cannot add an index to such a construct. If you need an index, create a regular view with the SELECT of your CTE, and make it an indexed view (by adding a clustered index to the view).
What is the difference between a temp table and a table variable?
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.
Can we join table with table variable?
f you are using a table variable in a join, you will need to alias the table in order to execute the query. You can use a table variable with dynamic SQL, but you must declare the table inside the dynamic SQL itself.
What is the difference between temp table and global temp table?
Local temp tables are only available to the SQL Server session or connection (means single user) that created the tables. ... A global temporary table remains in the database permanently, but the rows exist only within a given connection. When connection is closed, the data in the global temporary table disappears.
Can we use table variable in view?
There is certainly a good reason for views not supporting table variables. Table variables are only visible in the batch they are created in, and the CREATE VIEW statement must be in a batch of its own, so the table variable never exist when the CREATE VIEW statement runs.
What is a table variable?
Definition. The table variable is a special type of the local variable that helps to store data temporarily, similar to the temp table in SQL Server. In fact, the table variable provides all the properties of the local variable, but the local variables have some limitations, unlike temp or regular tables.
Can we create temp table in view?
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.
Do we need to drop table variable in SQL Server?
8 Answers. Table variables are automatically local and automatically dropped -- you don't have to worry about it. Table variables are just like int or varchar variables. ... The scope of a variable lasts from the point it is declared until the end of the batch or stored procedure in which it is declared.
How do you assign a table to a variable in SQL?
Insert for a Table Variable from a SQL Server Select Statement
- The first step appears in the first code block with a header comment of “declare table variable”. ...
- The second step in the code block is an INSERT statement that populates a table variable from the result set of a SELECT statement.
Can we create nonclustered index on table variable in SQL Server?
Inline index creation on table variables. The new syntax works on table variables, too! This means that with SQL Server 2014 and higher, you can create non-unique nonclustered indexes on table variables. You can even set the fillfactor option.
Can we create index on table variable in SQL Server?
Can I create a index on Name? Short answer: Yes. ... In SQL Server 2000 - 2012 indexes on table variables can only be created implicitly by creating a UNIQUE or PRIMARY KEY constraint. The difference between these constraint types are that the primary key must be on non nullable column(s).
Can we create indexes on table variables?
Creating an index on a table variable can be done implicitly within the declaration of the table variable by defining a primary key and creating unique constraints. The primary key will represent a clustered index, while the unique constraint a non clustered index.
What is clustered vs nonclustered index?
Clustered indexes only sort tables. Therefore, they do not consume extra storage. Non-clustered indexes are stored in a separate place from the actual table claiming more storage space. Clustered indexes are faster than non-clustered indexes since they don't involve any extra lookup step.
How do I create a temp table in SQL?
The Syntax to create a Temporary Table is given below:
- To Create Temporary Table: CREATE TABLE #EmpDetails (id INT, name VARCHAR(25))
- To Insert Values Into Temporary Table: INSERT INTO #EmpDetails VALUES (01, 'Lalit'), (02, 'Atharva')
- To Select Values from Temporary Table: SELECT * FROM #EmpDetails.
- Result: id. name. Lalit.
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