Check

CHECK (Domain Integrity Constraint)
Business rule validations can be applied to a table column by using  check constraint . CHECK constraints must be specified as a logical expression that evaluates either  to TRUE or FALSE
Restrictions:- A check constraints has the following limitations.

• The condition must be a Boolean expression that can be evaluated using the values in the row being inserted or updated.
• The condition cannot contain sub queries or sequences
• The condition cannot include SYSDATE, UID, USER or USERENV sql functions.

Syntax:- Columnname datatype(size) CHECK (logical expression)    à Column level
CHECK(logical expression),CHECK(logical expression),--   à Table level
Ex:-     1) create table product (pno number(5) CHECK(pno>100),na varchar2(20),
rate number(5));
insert into product values(101,’surf’,210);

• insert into product values(20,’cakes’,1200);

            2) Create table product1(pno number(5),na varchar2(20),
rate number(5),CHECK(na=UPPER(na)));
insert into product1 values(100,’OIL’,20);

• insert into product1 values(200,’cake’,30);

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