MySQL String Length
Summary: in this tutorial, you will learn about MySQL string length functions that allow you to get the length of strings measured in bytes and in characters.
MySQL supports various character sets such as latin1
, utf8
, etc. You use the SHOW CHARACTER SET
statement to get all character sets supported by the MySQL database server.
SHOW CHARACTER SET;
The Maxlen
column stores the number of bytes for character sets. In MySQL, a string can be in any character set. If a string contains 1-byte characters, its length measured in characters and its length measured in bytes is equal. However, if a string contains multi-byte characters, its length in bytes is typically greater than its length in characters.
To get the length of a string measured in bytes, you use the LENGTH
function as follows:
LENGTH(str);
You use the CHAR_LENGTH
function to get the length of a string measured in characters as follows:
CHAR_LENGTH(str);
Examples of LENGTH and CHAR_LENGTH functions
Let’s take a look at the following statements:
SET @s = CONVERT('MySQL String Length' USING ucs2);
SELECT CHAR_LENGTH(@s), LENGTH(@s);
How it works.
- First, we convert the
MySQL String Length
string intoucs2
character set, which isUCS-2
Unicode that holds 2-byte characters. - Second, we use the
CHAR_LENGTH
andLENGTH
functions to get the length ofthe @s
string in bytes and in characters. Because the@s
the string contains 2-byte characters, its length in character is 19, while its length in bytes is 38.
The following statements demonstrate how the LENGTH
and CHAR_LENGTH
functions that work with 1-byte characters:
SET @s = CONVERT('MySQL string length' USING latin1);
SELECT LENGTH(@s), CHAR_LENGTH(@s);
We use the latin1
character set for the @s
string. The latin1
the character set contains 1-byte characters; therefore, its length in bytes and its length in character are equal.
Notice that some character sets hold characters whose number of bytes can be varied e.g., for the utf8
character set:
SET @s = CONVERT('MySQL String Length' USING utf8);
SELECT CHAR_LENGTH(@s), LENGTH(@s);
The CHAR_LENGTH
and LENGTH
returns the same result. However, if a string has special characters, the result is different. See the following example:
SET @s = CONVERT('á' USING utf8);
SELECT CHAR_LENGTH(@s), LENGTH(@s);
An application of MySQL string length functions
Suppose we have a posts
the table that stores blog posts with four columns postid
, title
, excerpt
and content
. (We make the posts
table as simple as possible for the demonstration purpose).
First, we create the posts
table by using the CREATE TABLE statement:
CREATE TABLE posts(
postid int auto_increment primary key,
title varchar(255) NOT NULL,
excerpt varchar(255) NOT NULL,
content text,
pubdate datetime
)Engine=InnoDB;
Second, we insert some blog posts into the posts
table by using the INSERT statement:
INSERT INTO posts(title,excerpt,content)
VALUES('MySQL Length','MySQL string length function tutorial','dummy'),
('Second blog post','Second blog post','dummy');
We can use the CHAR_LENGTH
function to check if the except has more than 20 characters, we append an ellipsis (…) to the excerpt like the following query:
SELECT postid,
title,
IF(CHAR_LENGTH(excerpt) > 20,
CONCAT(LEFT(excerpt,20), '...'),
excerpt) summary
FROM posts;
In the SELECT statement, we use the IF
function to check if the length of the excerpt
the column is greater than 20, we concatenate the excerpt
with the ellipsis (…) by using the CONCAT
the statement, otherwise we just get the excerpt
.
In this tutorial, we have shown you how to use MySQL string length functions to get the length of a string in bytes and in characters.
Reference
- http://dev.mysql.com/doc/refman/5.7/en/string-functions.html#function_length – MySQL LENGTH function
- http://dev.mysql.com/doc/refman/5.7/en/string-functions.html#function_char-length – MySQL CHAR_LENGTH function
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