Aggregate functions operate on a column or column expression of a table or group (as created via GROUP BY clause).
For the examples below we use a simple table t(i int, c varchar(8)) with contents: INSERT into t(i,c) VALUES (1, 'one'), (2, 'two'), (3, 'tree'), (4, 'four'), (NULL, NULL); to create the shown Results.
| Function | Return type | Description | Example | Result |
|---|---|---|---|---|
| avg(numeric_expr) | double | compute the average of the non-NULL integer/float/decimal/month_interval values in the column or group | avg(i) | 2.5 |
| count(*) | bigint | count the number of rows in the column or group including those who may have NULL values | count(*) | 5 |
| count(col_expr) | bigint | count the number of non-NULL values in the column or group | count(i) | 4 |
| count(distinct col_expr) | bigint | count the number of distinct non-NULL values in the column or group | count(distinct i%2) | 2 |
| max(col_expr) | type of col_expr | return the maximum non-NULL value in the column or group | max(c) | two |
| min(col_expr) | type of col_expr | return the minimum non-NULL value in the column or group | min(c) | four |
| prod(numeric_expr) | bigint or hugeint or double | compute the product of the non-NULL numeric values in the column or group | prod(i) | 24 |
| prod(distinct numeric_expr) | bigint or hugeint or double | compute the product of the distinct non-NULL numeric values in the column or group | prod(distinct 1 + i%2) | 2 |
| sum(integer_expr) | bigint or hugeint | compute the sum of all non-NULL integer values in the column or group | sum(i) | 10 |
| sum(distinct integer_expr) | bigint or hugeint | compute the sum of all distinct non-NULL integer values in the column or group | sum(distinct i/2) | 3 |
| sum(decimal_expr) | decimal | compute the sum of all non-NULL decimal values in the column or group | sum(cast(i as decimal)) | 10.000 |
| sum(float_expr) | real or double | compute the sum of all non-NULL floating point values in the column or group | sum(cast(i as real)) | 10.0 |
| sum(month_interval_expr) | month_interval | compute the sum of all non-NULL interval month values in the column or group | sum(cast(i as interval month)) | 10 |
| sum(sec_interval_expr) | sec_interval | compute the sum of all non-NULL interval second values in the column or group | sum(cast(i as interval second)) | 10.000 |
Note: You must include the sys. or json. prefix for these aggregate functions (see examples) in order to work properly.
| Function | Return type | Description | Example | Result |
|---|---|---|---|---|
| listagg(col_expr) | varchar | concatenate non-NULL values in a column or group into one large varchar string with values separated by a comma (the default separator) Supported from release Jun2020 (11.37.7) | listagg(c) | one,two,tree,four |
| listagg(col_expr, separator_str) | varchar | concatenate non-NULL values in a column or group into one large varchar string with values separated by separator_str Supported from release Jun2020 (11.37.7) | listagg(i, ' | ') | 1 | 2 | 3 | 4 |
| sys.group_concat(col_expr) | clob | concatenate non-NULL values in a column or group into one large string with values separated by a comma (the default separator) | sys.group_concat(c) | one,two,tree,four |
| sys.group_concat(col_expr, separator_str) | clob | concatenate non-NULL values in a column or group into one large string with values separated by separator_str | sys.group_concat(i, ' | ') | 1 | 2 | 3 | 4 |
| json.tojsonarray(clob) | clob | convert string values in the column or group into a json array string | json.tojsonarray(c) | [ "one", "two", "tree", "four" ] |
| json.tojsonarray(double) | clob | convert numeric values in the column or group into a json array string | json.tojsonarray(i) | [ "1", "2", "3", "4" ] |
Note: You must include the sys. prefix for below aggregate functions (see examples) in order to work properly.
| Statistic Function | Return type | Description | Example | Result |
|---|---|---|---|---|
| sys.corr(numeric_a, numeric_b) | double | return the correlation coefficient of the non-NULL values in the numeric (integer/decimal/real/double) column or group numeric_a versus numeric_b | sys.corr(i, i+2) | 0.7500000000000001 |
| sys.covar_pop(numeric_a, numeric_b) | double | return the population covariance of numeric_expr of the non-NULL values in the numeric (integer/decimal/real/double/interval) column or group numeric_a versus numeric_b.Supported from release Jun2020 (11.37.7) | sys.covar_pop(i, i*2) | 2.5 |
| sys.covar_samp(numeric_a, numeric_b) | double | return the sample covariance of numeric_expr of the non-NULL values in the numeric (integer/decimal/real/double/interval) column or group numeric_a versus numeric_b.Supported from release Jun2020 (11.37.7) | sys.covar_samp(i, i*2) | 3.3333333333333335 |
| sys.median(col_expr) | type of col_expr | return the statistic median of the non-NULL values in the numeric (integer/decimal/real/double) or temporal (date/time/timestamp/interval) column or group | sys.median(i) | 2 |
| sys.median_avg(numeric_expr) | double | return the statistic median average of the non-NULL values in the numeric (integer/decimal/real/double) column or group | sys.median_avg(i) | 2.5 |
| sys.quantile(col_expr, percentile) | type of col_expr | return the statistic quantile of the non-NULL values in the numeric (integer/decimal/real/double) or temporal (date/time/timestamp/interval) column or group. The percentile argument must be between 0.0 and 1.0 | sys.quantile(i, 0.7) | 3 |
| sys.quantile_avg(numeric_expr, percentile) | double | return the statistic quantile average of the non-NULL values in the numeric (integer/decimal/real/double) column or group. The percentile argument must be between 0.0 and 1.0 | sys.quantile_avg(i, 0.6) | 2.8 |
| sys.stddev_pop(numeric_expr) | double | return the population standard deviation of numeric_expr of the non-NULL values in the numeric (integer/decimal/real/double/interval) column or group. Same as the square root of var_pop(). | sys.stddev_pop(i) | 1.118033988749895 |
| sys.stddev_samp(numeric_expr) | double | return the sample standard deviation of numeric_expr of the non-NULL values in the numeric (integer/decimal/real/double/interval) column or group. Same as the square root of var_samp(). | sys.stddev_samp(i) | 1.2909944487358056 |
| sys.var_pop(numeric_expr) | double | return the population standard variance of numeric_expr of the non-NULL values in the numeric (integer/decimal/real/double/interval) column or group. Same as the square of stddev_pop(). | sys.var_pop(i) | 1.25 |
| sys.var_samp(numeric_expr) | double | return the sample standard variance of numeric_expr of the non-NULL values in the numeric (integer/decimal/real/double/interval) column or group. Same as the square of stddev_samp(). | sys.var_samp(i) | 1.6666666666666667 |
You can also create your own aggregate functions, see Create Aggregate function command.
To list the available aggregate functions in your MonetDB server run query:
SELECT DISTINCT schema_id, name, func, mod, language, system FROM sys.functions WHERE type = 3 ORDER BY name;