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SQRT(x)

Returns the square root of x.
Example:
SELECT SQRT(9)
Result:

3

Example:

SELECT SQRT(-16)

Result:

NULL

STRCMP(string1, string2)

Returns 1 if string1 is the same as string2. If they are different, this function returns 0. A NULL value is
returned if either string is NULL.
Example:
SELECT STRCMP("Sandy", "Sandy")
Results:

1

Example:

SELECT STRCMP("Sandy", "Sandra")

Results:

0

Example:

SELECT STRCMP("Sandy", "sandy")

Results:

0

STD(expression) or STDDEV(expression)

Returns the standard deviation of the given expression. Only non NULL values are used to compute this
value.
Example:
SELECT STD(Quantity) FROM Orders
Results:

2.435

SUM(expression)

Returns the total sum of the given expression. Only non-NULL values are used to compute this value.
Example:
SELECT SUM(Cost) FROM Orders
Results:

10234.34

SUBSTRING_INDEX(x, y, z)

Returns a string from x after z occurrences of y have been found. If y is positive, everything to the left of the
final delimiter is returned. If y is negative, everything to the right is returned.
Example:
SELECT SUBSTRING_INDEX("mysql.3-23-3.Linux.tar.gz", ".", 3")
Result:

'mark@localhost'

Example:

SELECT SUBSTRING_INDEX("mysql.3-23-3.Linux.tar.gz", ".", -3")

Result:

"Linux.tar.gz"