## 8.10 Aggregate Functions

Aggregate functions operate on groups of records, rather than on individual records or variables.
They are often used in combination with a `GROUP BY`

clause.

### 8.10.1 `AVG()`

Available inDSQL, ESQL, PSQL

Syntax

`AVG ([ALL | DISTINCT] <expr>)`

`AVG`

Function ParametersParameter | Description |
---|---|

expr | Expression. It may contain a table column, a constant, a variable, an expression, a non-aggregate function or a UDF that returns a numeric data type. Aggregate functions are not allowed as expressions |

Result typeA numeric data type, the same as the data type of the argument.

Description`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`

.

Example

`SELECT`

`dept_no,`

`AVG(salary)`

`FROM employee`

`GROUP BY dept_no`

See also`SELECT`

### 8.10.2 `COUNT()`

Available inDSQL, ESQL, PSQL

Syntax

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

`COUNT`

Function ParametersParameter | Description |
---|---|

expr | Expression. It may contain a table column, a constant, a variable, an expression, a non-aggregate function or a UDF that returns a numeric data type. Aggregate functions are not allowed as expressions |

Result typeInteger

Description`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 definitioncounts 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.

Example

`SELECT`

`dept_no,`

`COUNT(*) AS cnt,`

`COUNT(DISTINCT name) AS cnt_name`

`FROM employee`

`GROUP BY dept_no`

See also`SELECT`

.

### 8.10.3 `LIST()`

Available inDSQL, PSQL

Changed in2.5

Syntax

`LIST ([ALL | DISTINCT] <expr> [, `*separator* ])

`LIST`

Function ParametersParameter | Description |
---|---|

expr | Expression.
It may contain a table column, a constant, a variable, an expression, a non-aggregate function or a UDF that returns the string data type or a |

separator | Optional alternative separator, a string expression. Comma is the default separator |

Result type`BLOB`

Description`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`BLOB`

s 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.

⚠︎CautionThis is a trick/workaround, and it depends on implementation details of the optimizer/execution order. This trick doesn’t always work, and it is not guaranteed to work across versions.

Retrieving the list, order undefined:

`SELECT LIST (display_name, '; ') FROM GR_WORK;`

Retrieving the list in alphabetical order, using a derived table:

`SELECT LIST (display_name, '; ')`

`FROM (SELECT display_name`

`FROM GR_WORK`

`ORDER BY display_name);`

See also`SELECT`

### 8.10.4 `MAX()`

Available inDSQL, ESQL, PSQL

Syntax

`MAX ([ALL | DISTINCT] <expr>)`

`MAX`

Function ParametersParameter | Description |
---|---|

expr | Expression. It may contain a table column, a constant, a variable, an expression, a non-aggregate function or a UDF. Aggregate functions are not allowed as expressions. |

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

Description`MAX`

returns the maximum non-`NULL`

element in the result set.

If the group is empty or contains only

`NULL`

s, 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

`BLOB`

s of any size and character set.

The `DISTINCT`

parameter makes no sense if used with `MAX()`

and is implemented only for compliance with the standard.

Example

`SELECT`

`dept_no,`

`MAX(salary)`

`FROM employee`

`GROUP BY dept_no`

See alsoSection 8.10.5, `MIN()`

, `SELECT`

### 8.10.5 `MIN()`

Available inDSQL, ESQL, PSQL

Syntax

`MIN ([ALL | DISTINCT] <expr>)`

`MIN`

Function ParametersParameter | Description |
---|---|

expr | Expression. It may contain a table column, a constant, a variable, an expression, a non-aggregate function or a UDF. Aggregate functions are not allowed as expressions. |

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

Description`MIN`

returns the minimum non-`NULL`

element in the result set.

If the group is empty or contains only

`NULL`

s, 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

`BLOB`

s of any size and character set.

The `DISTINCT`

parameter makes no sense if used with `MIN()`

and is implemented only for compliance with the standard.

Example

`SELECT`

`dept_no,`

`MIN(salary)`

`FROM employee`

`GROUP BY dept_no`

See alsoSection 8.10.4, `MAX()`

, `SELECT`

### 8.10.6 `SUM()`

Available inDSQL, ESQL, PSQL

Syntax

`SUM ([ALL | DISTINCT] <expr>)`

`SUM`

Function ParametersParameter | Description |
---|---|

expr | Numeric expression. It may contain a table column, a constant, a variable, an expression, a non-aggregate function or a UDF. Aggregate functions are not allowed as expressions. |

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

Description`SUM`

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

If the group is empty or contains only

`NULL`

s, 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.

Example

`SELECT`

`dept_no,`

`SUM (salary),`

`FROM employee`

`GROUP BY dept_no`

See also`SELECT`