SQL DDL Command
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Data Definition Language
SQL statements that can be used either interactively or within programming language source code to define databases and their components.
1. CREATE: used to create a table in database
Syntax: CREATE table table_name
(
attributes1 domain type
attributes2 domain type
.
.
.
attributes n domain type
);
2. ALTER: use to change the table definition i.e changing attribute definitions
i. To add new column in database:
Syntax:ALTER TABLE table_name
ADD column_name datatype;
Example: alter table student add address varchar(25)
ii. To modify datatypes of column:
Syntax:ALTER TABLE table_name ALTER Column column_name datatype;
Example:ALTER TABLE student ALTER Column phone bigint;
iii. To delete column from database:
Syntax:ALTER TABLE table_name DROP Column column_name;
Example: ALTER TABLE student DROP Column phone;
3. DROP: drop command delete the table from database
Syntax:DROP TABLE table_name;
Example: DROP TABLE student
4. TRUNCATE: used to delete all record of the given table
Syntax:TRUNCATE TABLE table_name;
Example: TRUNCATE TABLE student;
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