Database - Introduction to SQL - Discussion

Select * From Student
Where student_name like "kai%";

This is the select all student name where name starts with "kai".

Explain it answer clearly to get it.

"The wildcard in a WHERE clause" makes no sense whatsoever. The WHERE clause has not "wildcards". The LIKE operator supports wildcards, but not the WHERE clause (and together with CREATE the term wildcard makes even less sense).

Wild card basically use for missing character. Suppose there are 100 employee, and I want those employee whose name end with 'M' than I am writing like this:

Select EMP_NAME from EMPLOYEE where EMP_NAME like '%M';

Then I will get all employee name whose end character is M.

Hello friends,

Answer is an exact match is not possible in a select statements. Because if you want to display the name start with 'sa'. But unfortunately our database have 4 records start with sa. For this you write query like this select ename from emp where ename like 'sa%';

Here 4 records are displayed so we can't find the exact match.

Wildcard is use to find SUBSTRING.

There are 3 methods for using these,

1) % It substitutes zero or more character.

Eg: select * from details where city LIKE 'ber%';
->It returns citynames start with 'ber'.

2) _ it substitutes only 1 character.

Eg: select * from details where city LIKE '_erlin';
->It returns cityname start with any character followed by 'erlin'.

3) [charlist] Sets range of character.

Eg: select * from details where city LIKE '[a-c]%';
->It returns cityname start with a,b or c .

If we consider we have emp table with ename as column.

If we want to get names which starts with Letter B then
select * from emp where ename like '%B%'

If we want to get names which starts with Letter B and ends with E then
select * from emp where ename like 'B%E%'

If we want to get names which ends with Letter B then
select * from emp where ename like 'E%'

SQL wildcard('%') to find the entire search value or substring of the search value.It is like a grep command, which displays all results which matches that pattern.

For example if you have table student and want to display the student name ends with 'n' then the query will be:

SELECT * FROM STUDENT WHERE name LIKE '%n';

If you want to search name that have 'n' any where in the name:

SELECT * FROM STUDENT WHERE name LIKE '%n%';

Can you explain why Wildcard chars are used to replace any substring?

Can you explain with some more details?