SQL - Lecture 3 - Default Expression & Check Constraints - Oracle - Practical Demonstrations
This video demonstrates step by step implementation of default expression and check constraints in details.
Lecture Summary
DEFAULT is used to insert the default value.
If default is set into column then we can insert it in 2 ways.
1. Using Default keyword
2. By skipping the column at time of insert.
Check constraint
It is used to put validation on column for each row.
Syntax:
CHECK (condition)
Example
1. CHECK(CITY = 'RAJKOT')
2. CHECK(LENGTH(MOBILE)=10)
3. CHECK(EMAILID LIKE '___%@__%.__%')
4. CHECK(SUBSTR(NAME,1,1) BETWEEN 'A' AND 'P')
5 CHECK (CITY IN ('AHM', 'RJT', 'SURAT'))
Note
CONSTRAINT constraint_name is recommended for each constraints to identify constraints at the time of violations.
Constraint name is unique within the database.
Syntax of table
CREATE TABLE table_name(
col1 data_type [default expr] [ [constraint constraint_name] constraint_type ],
col2 data_type [default expr] [ [constraint constraint_name] constraint_type ],
.
.
colN data_type [default expr] [ [constraint constraint_name] constraint_type ], [table_level_constraint]
)
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