A check constraint can NOT be defined on a SQL View. SQL Check Constraint : In my previous article i have given idea of different types of constraints in SQL as well as SQL Not null Constraint with its examples. To create a check constraint, you define a logical expression that returns true or false. During my schooling, one of my teachers said, “A friend of mine scored 105 on a science test out of 100. To prevent this, the Age column should accept only positive numbers. Let us consider the age of an employee as an integer data type for a column in an employee table. The check constraint defined on a table must refer to only columns in that table. An Oracle check constraint allows you to enforce domain integrity by limiting the values accepted by one or more columns. One of the employees has entered the number -76 (negative 76) in the Age column. If you define a CHECK constraint on a single column it allows only certain values for this column.If you define a CHECK constraint on a table it can limit the values in certain columns based on values in other columns in the row.ORA-02290: check constraint (Amit.SYS_C004958) violatedTo allow naming of a CHECK constraint, and for defining a CHECK constraint on multiple columns, use the following SQL syntax:CONSTRAINT C_Student_Fees_Subject CHECK (Fees>500 AND Subject=’English’)INSERT INTO Student4A (Class, RollNo, Subject, Fees)ORA-02290: check constraint (Amit.C_STUDENT_FEES_SUBJECT) violatedCONSTRAINT C_Student4B_Fees_Subject CHECK (Fees>500 OR Subject=’English’)INSERT INTO Student4B (Class, RollNo, Subject, Fees)INSERT INTO Student4B (Class, RollNo, Subject, Fees)INSERT INTO Student4B (Class, RollNo, Subject, Fees)ORA-02290: check constraint (Amit.C_STUDENT4B_FEES_SUBJECT) violatedALTER TABLE Student MODIFY Class Number (10) CHECK (Class>5);To allow naming of a CHECK constraint, and for defining a CHECK constraint on multiple columns, use the following SQL syntax:ADD CONSTRAINT CONSTRAINT_TYPE (Column_Name);ADD CONSTRAINT C_Student_Subject_Fees CHECK (Subject=’Hindi’ AND Fees>500);ADD CONSTRAINT C_Student_Subject_Fees CHECK (Subject=’Hindi’ OR Fees>500);Hope you got the idea about the SQL Check Constraint with different real life examples. If you define a CHECK constraint on a table it can limit the values in certain columns based on values in other columns in the row. The CHECK constraint is used to limit the value range that can be placed in a column. In some contexts, there is a range of values defined, and no value should exceed the defined range.”The same concept applies to check constraints in SQL Server. Simply enabling is not enough. SQL constraints are used to specify rules for the data in a table. In this case, the value was inflated. It can not refer to columns in other tables. A check constraint can NOT include a SQL Subquery. Suppose in the Salary column we have inserted one wrong entry with a salary as $-2300.00. Let’s get started.For company ABC, as per their policies, employees must be 18 or older to work for them. In the context of age, it is not possible to have age in a negative number. This ensures the accuracy and reliability of the data in the table. Oracle uses this expression to validate the data that is being inserted or updated. SQL server will not raise any error because negative values are acceptable in an integer data type. Introduction to Oracle Check constraint. The condition CHECK(AGE >=18) adds a check constraint on the employee table with a condition where the age of an employee should be greater than or equal to 18.. We will try to insert some records to make sure our check constraint works. Vishwanath Dalvi is a gifted engineer and tech enthusiast. Hence, we will add a check constraint while creating the employee table to make sure the employees’ ages are always greater than or equal to 18.We will try to insert some records to make sure our check constraint works.SQL Server has raised the error below because Age = 15 is below the range defined in the CHECK constraint.Now, we want to make sure our Gender column only allows M (male) and F (female) values.Now, we will try inserting another character into the Gender column.What if we have already inserted some values which do not conform to the new check constraint?

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