SQL Like and Distinct Command

SQL Like Query

For wildcard filtering “Like ” operator is used. Within a search string, % means match any number of occurrences of any character. For example, to fetch all the employees starting with letter "J" from employee table given below, following SQL query is used.

Table Name: Employee

Employee_ID	Employee_Name	Age
1	John	28
2	Alex	24
3	James	35
4	Roy	22
5	Kay	44

select * from employee where employee_name like 'J%'

The result of the above given query is given below.

mployee_ID	Employee_Name	Age
1	John	28
3	James	35

To fetch all names containing letter a, following SQL query is used. This query will fetch all records having letter 'a' at any position. Please note that, like query is case sensitive.

select * from employee where employee_name like '%a%'

Employee_ID	Employee_Name	Age
3	James	35
5	Kay	44

To fetch all names ending with letter y, following SQL query is used.

select * from employee where employee_name like '%y'

Employee_ID	Employee_Name	Age
4	Roy	22
5	Kay	44

Points to be noted before using Like Operator

SQL 'Like' search takes more time to process. So before using like operator following tips should be considered.

• Don't overuse wildcards. If another search operator will do, use it instead.
• When you do use wildcards, try to not use them at the beginning of the search pattern unless absolutely necessary. Search patterns that begin with wildcards are the slowest to process.
• Pay careful attention to the placement of the wildcard symbols. If they are misplaced, you might not return the data you intended.

SQL Distinct Clause

SQL Distinct keyword is used to find unique values from specified column in a table or the number of rows that match a specific criterion. To select distinct prices from sales table given below

Table Name: Sales

Item	Quantity	Price	Reduction	Total
Item1	5	400	10	2000
Item2	6	300	10	1800
Item3	3	15	5	45
Item4	2	30	5	60
Item5	2	300	5	600
Item6	6	400	10	2400

Following SQL query is used to fetch unique prices from sales table.

select distinct(price) prices from SALES

Price
400
300
15
30