To find the square root value of a number in MySQL, you need to use the `SQRT()`

function.

The syntax of the `SQRT()`

function is as follows:

```
SQRT(expression)
```

The function will return the square root value of the expression passed into it. Only expressions that evaluate into numeric values are valid arguments for the function.

Here’s an example of the `SQRT()`

function in action:

```
SELECT SQRT(9);
-- +---------+
-- | SQRT(9) |
-- +---------+
-- | 3 |
-- +---------+
```

You can pass a literal numeric expression or a column name with a numeric type.

Suppose you have a table called `students`

with the following data:

```
+----+-------+-------+
| id | name | score |
+----+-------+-------+
| 1 | Jack | 72 |
| 2 | Susan | 48 |
| 3 | John | 56 |
| 4 | Fany | 81 |
+----+-------+-------+
```

You can pass the `score`

column into the `SQRT()`

function as shown below:

```
SELECT SQRT(score) FROM students;
-- +-------------------+
-- | SQRT(score) |
-- +-------------------+
-- | 8.48528137423857 |
-- | 6.928203230275509 |
-- | 7.483314773547883 |
-- | 9 |
-- +-------------------+
```

When you pass a non-numeric expression, the function will return a `0`

value.

When you pass a negative number, then `SQRT()`

function will return a `NULL`

value

```
SELECT SQRT(false), SQRT("a string"), SQRT(-9);
-- +-------------+------------------+----------+
-- | SQRT(false) | SQRT("a string") | SQRT(-9) |
-- +-------------+------------------+----------+
-- | 0 | 0 | NULL |
-- +-------------+------------------+----------+
```

And that’s how you can find the square root value of a number in MySQL.

You can pass an expression that evaluates to a numeric value or a table column name with numeric type.