Name
CONCAT()
Synopsis
CONCAT(string
, ...)
With this function, strings or columns can be concatenated or pasted together into one resulting field. Any number of strings may be specified, with each argument separated by a comma. If any of the values given are NULL, a NULL value is returned. Here is an example:
SELECT CONCAT(name_first, ' ', name_last) AS Student FROM students WHERE name_last = 'Dyer'; +-------------------+ | Student | +-------------------+ | Kenneth Dyer | | Geoffrey Dyer | | Marie Dyer | | NULL | +-------------------+
In this example, the database contained four students with the
last name Dyer, but one of them had a NULL value
in the name_first
column. Within the parentheses of
the function, notice that a space is given within quotes as the second
element so that the results show a space between each student’s first
and last name.
Another use for CONCAT()
is to convert
numeric values of a given column to strings. This may be useful when
working with an API such as Perl and when using
UNION
to mix data from two different data
types.
Here is an example:
SELECT CONCAT(type_id) AS id, type AS title FROM types UNION SELECT topic_id AS id, topic AS title FROM topics;
In this example, the column type_id
is an
INT
, whereas the column topic_id
is a CHAR
column. In MySQL, the results can be mixed. However, if this SQL statement is used to create a hash of data in Perl or another API language, you may encounter problems retrieving data. In order that the data in the columns agree, ...
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