9.2 General-purpose Aggregate Functions

9.2.1 AVG()

Available inDSQL, ESQL, PSQL

Result typeDepends on the input type

Syntax

1. AVG ([ALL | DISTINCT] <expr>)

Table 9.2.1.1 AVG Function Parameters

AVG returns the average argument value in the group. NULL is ignored.

• Parameter ALL (the default) applies the aggregate function to all values.
• Parameter DISTINCT directs the AVG function to consider only one instance of each unique value, no matter how many times this value occurs.
• If the set of retrieved records is empty or contains only NULL, the result will be NULL.

The result type of AVG depends on the input type:

Note

In Firebird 4.0.0, the result type is determined the same as Section 9.2.6, SUM(). This was fixed in 4.0.1, see firebird#6845.

9.2.1.1 AVG Examples

1. SELECT
2. dept_no,
3. AVG(salary)
4. FROM employee
5. GROUP BY dept_no

See alsoSELECT

9.2.2 COUNT()

Available inDSQL, ESQL, PSQL

Result typeBIGINT

Syntax

1. COUNT ([ALL | DISTINCT] <expr> | *)

Table 9.2.2.1 COUNT Function Parameters

COUNT returns the number of non-null values in a group.

• ALL is the default: it simply counts all values in the set that are not NULL.
• If DISTINCT is specified, duplicates are excluded from the counted set.

• If COUNT (*) is specified instead of the expression expr, all rows will be counted. COUNT (*) —

• does not accept parameters

• cannot be used with the keyword DISTINCT
• does not take an expr argument, since its context is column-unspecific by definition
• counts each row separately and returns the number of rows in the specified table or group without omitting duplicate rows
• counts rows containing NULL
• If the result set is empty or contains only NULL in the specified column(s), the returned count is zero.

9.2.2.1 COUNT Examples

1. SELECT
2. dept_no,
3. COUNT(*) AS cnt,
4. COUNT(DISTINCT name) AS cnt_name
5. FROM employee
6. GROUP BY dept_no

See alsoSELECT.

9.2.3 LIST()

Available inDSQL, PSQL

Result typeBLOB

Syntax

1. LIST ([ALL | DISTINCT] <expr> [, separator ])

Table 9.2.3.1 LIST Function Parameters

LIST returns a string consisting of the non-NULL argument values in the group, separated either by a comma or by a user-supplied separator. If there are no non-NULL values (this includes the case where the group is empty), NULL is returned.

• ALL (the default) results in all non-NULL values being listed. With DISTINCT, duplicates are removed, except if expr is a BLOB.
• In Firebird 2.5 and up, the optional separator argument may be any string expression. This makes it possible to specify e.g. ascii_char(13) as a separator. (This improvement has also been backported to 2.1.4.)
• The expr and separator arguments support BLOBs of any size and character set.
• Date/time and numeric arguments are implicitly converted to strings before concatenation.
• The result is a text BLOB, except when expr is a BLOB of another subtype.
• The ordering of the list values is undefined — the order in which the strings are concatenated is determined by read order from the source set which, in tables, is not generally defined. If ordering is important, the source data can be pre-sorted using a derived table or similar.

9.2.3.1 LIST Examples

1. Retrieving the list, order undefined:

1. SELECT LIST (display_name, '; ') FROM GR_WORK; 2. Retrieving the list in alphabetical order, using a derived table:

1. SELECT LIST (display_name, '; ') 2. FROM (SELECT display_name 3. FROM GR_WORK 4. ORDER BY display_name);

See alsoSELECT

9.2.4 MAX()

Available inDSQL, ESQL, PSQL

Result typeReturns a result of the same data type the input expression.

Syntax

1. MAX ([ALL | DISTINCT] <expr>)

Table 9.2.4.1 MAX Function Parameters

MAX returns the maximum non-NULL element in the result set.

• If the group is empty or contains only NULLs, the result is NULL.
• If the input argument is a string, the function will return the value that will be sorted last if COLLATE is used.
• This function fully supports text BLOBs of any size and character set.

Note

The DISTINCT parameter makes no sense if used with MAX() and is implemented only for compliance with the standard.

9.2.4.1 MAX Examples

1. SELECT
2. dept_no,
3. MAX(salary)
4. FROM employee
5. GROUP BY dept_no

See alsoSection 9.2.5, MIN(), SELECT

9.2.5 MIN()

Available inDSQL, ESQL, PSQL

Result typeReturns a result of the same data type the input expression.

Syntax

1. MIN ([ALL | DISTINCT] <expr>)

Table 9.2.5.1 MIN Function Parameters

MIN returns the minimum non-NULL element in the result set.

• If the group is empty or contains only NULLs, the result is NULL.
• If the input argument is a string, the function will return the value that will be sorted first if COLLATE is used.
• This function fully supports text BLOBs of any size and character set.

Note

The DISTINCT parameter makes no sense if used with MIN() and is implemented only for compliance with the standard.

9.2.5.1 MIN Examples

1. SELECT
2. dept_no,
3. MIN(salary)
4. FROM employee
5. GROUP BY dept_no

See alsoSection 9.2.4, MAX(), SELECT

9.2.6 SUM()

Available inDSQL, ESQL, PSQL

Result typeDepends on the input type

Syntax

1. SUM ([ALL | DISTINCT] <expr>)

Table 9.2.6.1 SUM Function Parameters

SUM calculates and returns the sum of non-null values in the group.

• If the group is empty or contains only NULLs, the result is NULL.
• ALL is the default option — all values in the set that are not NULL are processed. If DISTINCT is specified, duplicates are removed from the set and the SUM evaluation is done afterwards.

The result type of SUM depends on the input type:

9.2.6.1 SUM Examples

1. SELECT
2. dept_no,
3. SUM (salary),
4. FROM employee
5. GROUP BY dept_no

See alsoSELECT