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How to Calculate a Square Root in SQL

  • SQRT

Problem:

You want to find the square root of a number in SQ:.

Example:

You want to compute the square root of all numbers in the column number from the table data.

number
9
2
1
0.25
0
-4

Solution:

SELECT
  number,
  SQRT(number) AS square_root
FROM data;

The result is:

numbersquare_root
93
21.4142135623731
11
0.250.5
00
-4error

Discussion:

To compute the square root of a number in SQL, use the SQRT() function. This function takes a number as its argument and returns the square root.

Note that there is no real square root from a negative number (complex numbers aren't supported) – hence the error.

Also, for most numbers (e.g., 2, 2.5, 3, 3.2 etc.) the square root is an irrational number – in the square_root column you won't see the exact results, only the first several digits of their decimal expansion.

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