AVG aggregate function

The AVG function returns the average of a set of numbers.

Note: The result of the function can be affected by the enablement of the large_aggregation configuration parameter.

The schema is SYSIBM.

expression: An expression that returns a set of built-in numeric values. The AVG function ignores any null values the input expression might contain.
ALL or DISTINCT: If ALL is specified, all values returned by the expression, including duplicate values, are used to calculate the average (this is the default). If DISTINCT is specified, duplicate values are ignored. Decimal floating-point values that are numerically equal are treated as duplicates even if they have different numbers of significant digits. For example, if the set of values returned by an expression includes the decimal floating-point numbers 123, 123.0, and 123.00, only one of these values is used to calculate the average.

Result

The data type of the result is the same as the data type of the input expression, with the following exceptions:

If the data type of the input expression is BOOLEAN, SMALLINT, INTEGER, or BIGINT, the data type of the result is DECIMAL(31,6).
If the data type of the input expression is single-precision floating point (REAL), the data type of the result is double-precision floating point (DOUBLE).
If the data type of the input expression is DECFLOAT(n), the data type of the result is DECFLOAT(34).
If the input expression is a DECIMAL value with precision p and scale s, the result is a DECIMAL value with precision 31 and scale 31 - p + s.

During evaluation, the order in which the input values are added together is undefined, but every intermediate result must be within the range of the data type of the result.

The result can be null. If the function is applied to an empty set, the result is a null value; otherwise, the result is the average value of the set.

Examples

Example 1: Using the PROJECT table, set the host variable AVERAGE (decimal(5,2)) to the average staffing level (PRSTAFF) of projects in department (DEPTNO) 'D11'.
```
   SELECT AVG(PRSTAFF)
     INTO :AVERAGE
     FROM PROJECT
     WHERE DEPTNO = 'D11'
```
Results in AVERAGE being set to 4.25 (that is 17/4) when using the sample table.
Example 2: Using the PROJECT table, set the host variable ANY_CALC (decimal(5,2)) to the average of each unique staffing level value (PRSTAFF) of projects in department (DEPTNO) 'D11'.
```
   SELECT AVG(DISTINCT PRSTAFF)
     INTO :ANY_CALC
     FROM PROJECT
     WHERE DEPTNO = 'D11'
```
Results in ANY_CALC being set to 4.66 (that is 14/3) when using the sample table.