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| <!DOCTYPE concept PUBLIC "-//OASIS//DTD DITA Concept//EN" "concept.dtd"> |
| <concept id="sum"> |
| |
| <title>SUM Function</title> |
| <titlealts audience="PDF"><navtitle>SUM</navtitle></titlealts> |
| <prolog> |
| <metadata> |
| <data name="Category" value="Impala"/> |
| <data name="Category" value="SQL"/> |
| <data name="Category" value="Impala Functions"/> |
| <data name="Category" value="Analytic Functions"/> |
| <data name="Category" value="Aggregate Functions"/> |
| <data name="Category" value="Querying"/> |
| <data name="Category" value="Developers"/> |
| <data name="Category" value="Data Analysts"/> |
| </metadata> |
| </prolog> |
| |
| <conbody> |
| |
| <p> |
| <indexterm audience="hidden">sum() function</indexterm> |
| An aggregate function that returns the sum of a set of numbers. Its single argument can be numeric column, or |
| the numeric result of a function or expression applied to the column value. Rows with a <codeph>NULL</codeph> |
| value for the specified column are ignored. If the table is empty, or all the values supplied to |
| <codeph>MIN</codeph> are <codeph>NULL</codeph>, <codeph>SUM</codeph> returns <codeph>NULL</codeph>. |
| </p> |
| |
| <p conref="../shared/impala_common.xml#common/syntax_blurb"/> |
| |
| <codeblock>SUM([DISTINCT | ALL] <varname>expression</varname>) [OVER (<varname>analytic_clause</varname>)]</codeblock> |
| |
| <p> |
| When the query contains a <codeph>GROUP BY</codeph> clause, returns one value for each combination of |
| grouping values. |
| </p> |
| |
| <p> |
| <b>Return type:</b> <codeph>BIGINT</codeph> for integer arguments, <codeph>DOUBLE</codeph> for floating-point |
| arguments |
| </p> |
| |
| <p conref="../shared/impala_common.xml#common/complex_types_blurb"/> |
| |
| <p conref="../shared/impala_common.xml#common/complex_types_aggregation_explanation"/> |
| |
| <p conref="../shared/impala_common.xml#common/complex_types_aggregation_example"/> |
| |
| <p conref="../shared/impala_common.xml#common/example_blurb"/> |
| |
| <p> |
| The following example shows how to use <codeph>SUM()</codeph> to compute the total for all the values in the |
| table, a subset of values, or the sum for each combination of values in the <codeph>GROUP BY</codeph> clause: |
| </p> |
| |
| <codeblock>-- Total all the values for this column in the table. |
| select sum(c1) from t1; |
| -- Find the total for this column from a subset of the table. |
| select sum(c1) from t1 where month = 'January' and year = '2013'; |
| -- Find the total from a set of numeric function results. |
| select sum(length(s)) from t1; |
| -- Often used with functions that return predefined values to compute a score. |
| select sum(case when grade = 'A' then 1.0 when grade = 'B' then 0.75 else 0) as class_honors from test_scores; |
| -- Can also be used in combination with DISTINCT and/or GROUP BY. |
| -- Return more than one result. |
| select month, year, sum(purchase_price) from store_stats group by month, year; |
| -- Filter the input to eliminate duplicates before performing the calculation. |
| select sum(distinct x) from t1; |
| </codeblock> |
| |
| <p rev="2.0.0"> |
| The following examples show how to use <codeph>SUM()</codeph> in an analytic context. They use a table |
| containing integers from 1 to 10. Notice how the <codeph>SUM()</codeph> is reported for each input value, as |
| opposed to the <codeph>GROUP BY</codeph> clause which condenses the result set. |
| <codeblock>select x, property, sum(x) <b>over (partition by property)</b> as sum from int_t where property in ('odd','even'); |
| +----+----------+-----+ |
| | x | property | sum | |
| +----+----------+-----+ |
| | 2 | even | 30 | |
| | 4 | even | 30 | |
| | 6 | even | 30 | |
| | 8 | even | 30 | |
| | 10 | even | 30 | |
| | 1 | odd | 25 | |
| | 3 | odd | 25 | |
| | 5 | odd | 25 | |
| | 7 | odd | 25 | |
| | 9 | odd | 25 | |
| +----+----------+-----+ |
| </codeblock> |
| |
| Adding an <codeph>ORDER BY</codeph> clause lets you experiment with results that are cumulative or apply to a moving |
| set of rows (the <q>window</q>). The following examples use <codeph>SUM()</codeph> in an analytic context |
| (that is, with an <codeph>OVER()</codeph> clause) to produce a running total of all the even values, |
| then a running total of all the odd values. The basic <codeph>ORDER BY x</codeph> clause implicitly |
| activates a window clause of <codeph>RANGE BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW</codeph>, |
| which is effectively the same as <codeph>ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW</codeph>, |
| therefore all of these examples produce the same results: |
| <codeblock>select x, property, |
| sum(x) over (partition by property <b>order by x</b>) as 'cumulative total' |
| from int_t where property in ('odd','even'); |
| +----+----------+------------------+ |
| | x | property | cumulative total | |
| +----+----------+------------------+ |
| | 2 | even | 2 | |
| | 4 | even | 6 | |
| | 6 | even | 12 | |
| | 8 | even | 20 | |
| | 10 | even | 30 | |
| | 1 | odd | 1 | |
| | 3 | odd | 4 | |
| | 5 | odd | 9 | |
| | 7 | odd | 16 | |
| | 9 | odd | 25 | |
| +----+----------+------------------+ |
| |
| select x, property, |
| sum(x) over |
| ( |
| partition by property |
| <b>order by x</b> |
| <b>range between unbounded preceding and current row</b> |
| ) as 'cumulative total' |
| from int_t where property in ('odd','even'); |
| +----+----------+------------------+ |
| | x | property | cumulative total | |
| +----+----------+------------------+ |
| | 2 | even | 2 | |
| | 4 | even | 6 | |
| | 6 | even | 12 | |
| | 8 | even | 20 | |
| | 10 | even | 30 | |
| | 1 | odd | 1 | |
| | 3 | odd | 4 | |
| | 5 | odd | 9 | |
| | 7 | odd | 16 | |
| | 9 | odd | 25 | |
| +----+----------+------------------+ |
| |
| select x, property, |
| sum(x) over |
| ( |
| partition by property |
| <b>order by x</b> |
| <b>rows between unbounded preceding and current row</b> |
| ) as 'cumulative total' |
| from int_t where property in ('odd','even'); |
| +----+----------+------------------+ |
| | x | property | cumulative total | |
| +----+----------+------------------+ |
| | 2 | even | 2 | |
| | 4 | even | 6 | |
| | 6 | even | 12 | |
| | 8 | even | 20 | |
| | 10 | even | 30 | |
| | 1 | odd | 1 | |
| | 3 | odd | 4 | |
| | 5 | odd | 9 | |
| | 7 | odd | 16 | |
| | 9 | odd | 25 | |
| +----+----------+------------------+ |
| </codeblock> |
| |
| Changing the direction of the <codeph>ORDER BY</codeph> clause causes the intermediate |
| results of the cumulative total to be calculated in a different order: |
| |
| <codeblock>select sum(x) over (partition by property <b>order by x desc</b>) as 'cumulative total' |
| from int_t where property in ('odd','even'); |
| +----+----------+------------------+ |
| | x | property | cumulative total | |
| +----+----------+------------------+ |
| | 10 | even | 10 | |
| | 8 | even | 18 | |
| | 6 | even | 24 | |
| | 4 | even | 28 | |
| | 2 | even | 30 | |
| | 9 | odd | 9 | |
| | 7 | odd | 16 | |
| | 5 | odd | 21 | |
| | 3 | odd | 24 | |
| | 1 | odd | 25 | |
| +----+----------+------------------+ |
| </codeblock> |
| |
| The following examples show how to construct a moving window, with a running total taking into account 1 row before |
| and 1 row after the current row, within the same partition (all the even values or all the odd values). |
| Because of a restriction in the Impala <codeph>RANGE</codeph> syntax, this type of |
| moving window is possible with the <codeph>ROWS BETWEEN</codeph> clause but not the <codeph>RANGE BETWEEN</codeph> |
| clause: |
| <codeblock>select x, property, |
| sum(x) over |
| ( |
| partition by property |
| <b>order by x</b> |
| <b>rows between 1 preceding and 1 following</b> |
| ) as 'moving total' |
| from int_t where property in ('odd','even'); |
| +----+----------+--------------+ |
| | x | property | moving total | |
| +----+----------+--------------+ |
| | 2 | even | 6 | |
| | 4 | even | 12 | |
| | 6 | even | 18 | |
| | 8 | even | 24 | |
| | 10 | even | 18 | |
| | 1 | odd | 4 | |
| | 3 | odd | 9 | |
| | 5 | odd | 15 | |
| | 7 | odd | 21 | |
| | 9 | odd | 16 | |
| +----+----------+--------------+ |
| |
| -- Doesn't work because of syntax restriction on RANGE clause. |
| select x, property, |
| sum(x) over |
| ( |
| partition by property |
| <b>order by x</b> |
| <b>range between 1 preceding and 1 following</b> |
| ) as 'moving total' |
| from int_t where property in ('odd','even'); |
| ERROR: AnalysisException: RANGE is only supported with both the lower and upper bounds UNBOUNDED or one UNBOUNDED and the other CURRENT ROW. |
| </codeblock> |
| </p> |
| |
| <p conref="../shared/impala_common.xml#common/restrictions_blurb"/> |
| |
| <!-- This conref appears under SUM(), AVG(), FLOAT, and DOUBLE topics. --> |
| |
| <p conref="../shared/impala_common.xml#common/sum_double"/> |
| |
| <p conref="../shared/impala_common.xml#common/related_info"/> |
| |
| <p> |
| <xref href="impala_analytic_functions.xml#analytic_functions"/> |
| </p> |
| |
| </conbody> |
| </concept> |