SQL LIKE Operator

The LIKE operator is used to list all rows in a table whose column values match a specified pattern. It is useful when you want to search rows to match a specific pattern, or when you do not know the entire value. For this purpose we use a wildcard character '%'.

For example: To select all the students whose name begins with 'S'

SELECT first_name, last_name
FROM student_details
WHERE first_name LIKE 'S%';

The output would be similar to:

first_name	last_name
-------------	-------------
Stephen	Fleming
Shekar	Gowda

The above select statement searches for all the rows where the first letter of the column first_name is 'S' and rest of the letters in the name can be any character.

There is another wildcard character you can use with LIKE operator. It is the underscore character, ' _ ' . In a search string, the underscore signifies a single character.

For example: to display all the names with 'a' second character,

SELECT first_name, last_name
FROM student_details
WHERE first_name LIKE '_a%'; 

The output would be similar to:

first_name	last_name
-------------	-------------
Rahul	Sharma

NOTE:Each underscore act as a placeholder for only one character. So you can use more than one underscore. Eg: ' __i% '-this has two underscores towards the left, 'S__j%' - this has two underscores between character 'S' and 'i'.

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The LIKE condition allows you to use wildcards in the where clause of an SQL statement. This allows you to perform pattern matching. The LIKE condition can be used in any valid SQL statement - select, insert, update, or delete.
The patterns that you can choose from are:
% allows you to match any string of any length (including zero length)
_ allows you to match on a single character

Examples using % wildcard

The first example that we'll take a look at involves using % in the where clause of a select statement. We are going to try to find all of the suppliers whose name begins with 'Hew'.
SELECT * FROM suppliers
WHERE supplier_name like 'Hew%';
You can also using the wildcard multiple times within the same string. For example,
SELECT * FROM suppliers
WHERE supplier_name like '%bob%';
In this example, we are looking for all suppliers whose name contains the characters 'bob'.
You could also use the LIKE condition to find suppliers whose name does not start with 'T'. For example,
SELECT * FROM suppliers
WHERE supplier_name not like 'T%';
By placing the not keyword in front of the LIKE condition, you are able to retrieve all suppliers whose name does not start with 'T'.

Examples using _ wildcard

Next, let's explain how the _ wildcard works. Remember that the _ is looking for only one character.
For example,
SELECT * FROM suppliers
WHERE supplier_name like 'Sm_th';
This SQL statement would return all suppliers whose name is 5 characters long, where the first two characters is 'Sm' and the last two characters is 'th'. For example, it could return suppliers whose name is 'Smith', 'Smyth', 'Smath', 'Smeth', etc.
Here is another example,
SELECT * FROM suppliers
WHERE account_number like '12317_';
You might find that you are looking for an account number, but you only have 5 of the 6 digits. The example above, would retrieve potentially 10 records back (where the missing value could equal anything from 0 to 9). For example, it could return suppliers whose account numbers are:
123170
123171
123172
123173
123174
123175
123176
123177
123178
123179.

Examples using Escape Characters

Next, in Oracle, let's say you wanted to search for a % or a _ character in a LIKE condition. You can do this using an Escape character.
Please note that you can define an escape character as a single character (length of 1) ONLY.
For example,
SELECT * FROM suppliers
WHERE supplier_name LIKE '!%' escape '!';
This SQL statement identifies the ! character as an escape character. This statement will return all suppliers whose name is %.
Here is another more complicated example:
SELECT * FROM suppliers
WHERE supplier_name LIKE 'H%!%' escape '!';
This example returns all suppliers whose name starts with H and ends in %. For example, it would return a value such as 'Hello%'.
You can also use the Escape character with the _ character. For example,
SELECT * FROM suppliers
WHERE supplier_name LIKE 'H%!_' escape '!';
This example returns all suppliers whose name starts with H and ends in _. For example, it would return a value such as 'Hello_'.