alter command is used
for altering the table structure
, such as, to add a column to existing table. to rename any existing column. to change datatype of any column or to modify its size.
What is the ALTER command?
ALTER Command is
used to add, delete, modify the attributes of the relations (tables) in the database
. UPDATE Command is used to update existing records in a database.
What is an ALTER command explain with example?
The SQL ALTER TABLE command is
used to add, delete or modify columns in an existing table
. You should also use the ALTER TABLE command to add and drop various constraints on an existing table.
What ALTER do in SQL?
ALTER TABLE is
used to add, delete/drop or modify columns in the existing table
. It is also used to add and drop various constraints on the existing table. ADD is used to add columns into the existing table.
What is the use of ALTER in database?
ALTER DATABASE
enables you to change the overall characteristics of a database
. These characteristics are stored in the data dictionary. This statement requires the ALTER privilege on the database. ALTER SCHEMA is a synonym for ALTER DATABASE .
What is DELETE command?
The DELETE command is
used to delete specified rows(one or more)
. While this command is used to delete all the rows from a table. 2. It is a DML(Data Manipulation Language) command.
Is DELETE a DDL command?
DROP and TRUNCATE are DDL commands, whereas DELETE is a
DML command
. DELETE operations can be rolled back (undone), while DROP and TRUNCATE operations cannot be rolled back.
How do you use alter query?
- SQL Server / MS Access: ALTER TABLE table_name. ALTER COLUMN column_name datatype;
- My SQL / Oracle (prior version 10G): ALTER TABLE table_name. MODIFY COLUMN column_name datatype;
- Oracle 10G and later: ALTER TABLE table_name.
What is the use of DROP command?
DROP is used
to delete a whole database or just a table
. The DROP statement destroys the objects like an existing database, table, index, or view. A DROP statement in SQL removes a component from a relational database management system (RDBMS).
Is insert a DDL command?
| DDL DML | Basic command present in DDL are CREATE, DROP, RENAME, ALTER etc. BASIC command present in DML are UPDATE, INSERT, MERGE etc. |
|---|
What is trigger in SQL?
A SQL trigger is
a database object which fires when an event occurs in a database
. We can execute a SQL query that will “do something” in a database when a change occurs on a database table such as a record is inserted or updated or deleted. For example, a trigger can be set on a record insert in a database table.
What are the DDL commands in SQL?
DDL (Data Definition Language):
List of DDL commands:
CREATE: This command is used to create the database or its
objects (like table, index, function, views, store procedure, and triggers). DROP: This command is used to delete objects from the database. ALTER: This is used to alter the structure of the database.
What is primary key SQL?
In SQL, a primary key is
a single field or combination of fields that uniquely defines a record
. None of the fields that are part of the primary key can contain a NULL value. A table can have only one primary key. You use either the CREATE TABLE statement or the ALTER TABLE statement to create a primary key in SQL.
What is drop in database?
Dropping a database
deletes the database from an instance of SQL Server and deletes the physical disk files used by the database
. If the database or any one of its files is offline when it is dropped, the disk files are not deleted. These files can be deleted manually by using Windows Explorer.
How do you alter a database?
In SQL 2012 the
alter command
modifies a database or the file and filegroups which are associated with the database. You can add or remove files from as database, changes the attributes of a database or its files and filegroups, changes the database collation, and sets database options.
How do I edit a SQL database?
- In Object Explorer, expand the database that contains the view and then expand Views.
- Right-click the view and select Edit Top 200 Rows.
- You may need to modify the SELECT statement in the SQL pane to return the rows to be modified.
