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String Functions

In SQL, you can perform various operations on strings, including extracting a string, combining two or more strings, and converting a case of a string.

CONCAT Function​

The CONCAT function combines two or more strings into one string. The following is the syntax:

CONCAT(string1, string2, ...., string_n)

Example:

SELECT CONCAT('Hello ', 'World');

The output of the above SQL statement will be 'Hello World'.

SUBSTRING Function​

The SUBSTRING function extracts a string from a given string. The syntax looks as follows:

SUBSTRING(string, start, length)

Example:

SELECT SUBSTRING('SQL Tutorial', 1, 3);

The output of the above query will be 'SQL'.

LENGTH Function​

The LENGTH function returns the length of a string. The syntax is:

LENGTH(string)

Example:

SELECT LENGTH('Hello World');

The output of the above SQL statement will be 11.

UPPER and LOWER Function​

The UPPER function converts all the letters in a string to uppercase, whereas the LOWER function to lowercase.

Syntax:

UPPER(string)

LOWER(string)

Examples:

SELECT UPPER('Hello World');

SELECT LOWER('Hello World');

The output of the above SQL statements will be 'HELLO WORLD' and 'hello world' respectively.

TRIM Function​

The TRIM function removes leading and trailing spaces of a string. You can also remove other specified characters.

Syntax:

TRIM([LEADING|TRAILING|BOTH] [removal_string] FROM original_string)

Example:

SELECT TRIM('   Hello World   ');
SELECT TRIM('h' FROM 'hello');

The output of the first query will be 'Hello World' and that of the second query will be 'ello'.