Functions
MySQL provides built-in functions that perform special operations.
Aggregate Functions
Aggregate functions operate on a set of data. These are usually used to perform some action on a complete set of returned rows. For example, SELECT AVG(height) FROM kids
would return the average of all the values of the height
field in the kids
table. AVG( )
, COUNT( )
, and SUM( )
allow DISTINCT
.
AVG(
expression)
Returns the average value of the values in expression (e.g.,
SELECT AVG(score) FROM tests
).BIT_AND(
expression)
Returns the bitwise
AND
aggregate of all the values in expression (e.g.,SELECT BIT_AND(flags) FROM options
). A bit will be set in the result if and only if the bit is set in every input field.BIT_OR(
expression
)
Returns the bitwise
OR
aggregate of all the values inexpression
(e.g.,SELECT BIT_OR(flags) FROM options
). A bit is set in the result if it is set in at least one of the input fields.BIT_XOR(
expression
)
Returns the bitwise
XOR
aggregate of all the values inexpression
with 64-bit precision.COUNT(
expression
)
Returns the number of times
expression
was not null.COUNT(*)
will return the number of rows with some data in the entire table (e.g.,SELECT COUNT(*) FROM folders
).GROUP_CONCAT([DISTNCT]
expression
[ORDER BY {
column
|
expression
}] [SEPARATOR
sep
])
Provides a string that combines in order all the results marked by
expression
.MAX(
expression
)
Returns the largest value in
expression
(e.g.,SELECT MAX (elevation) FROM mountains
).MIN(
expression
)
Returns the smallest value ...
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