Amazon DynamoDB

SELECT Statements

A SELECT statement can consist of the following basic clauses.

  • SELECT

  • INTO

  • FROM

  • JOIN

  • WHERE

  • GROUP BY

  • HAVING

  • UNION

  • ORDER BY

  • LIMIT

SELECT Syntax

The following syntax diagram outlines the syntax supported by the SQL engine of the provider:

SELECT {

[ TOP <numeric_literal> | DISTINCT ]

{

*

| {

<expression> [ [ AS ] <column_reference> ]

| { <table_name> | <correlation_name> } .*

} [ , ... ]

}

[ INTO csv:// [ filename= ] <file_path> [ ;delimiter=tab ] ]

{

FROM <table_reference> [ [ AS ] <identifier> ]

} [ , ... ]

[ [

INNER | { { LEFT | RIGHT | FULL } [ OUTER ] }

] JOIN <table_reference> [ ON <search_condition> ] [ [ AS ] <identifier> ]

] [ ... ]

[ WHERE <search_condition> ]

[ GROUP BY <column_reference> [ , ... ]

[ HAVING <search_condition> ]

[ UNION [ ALL ] <select_statement> ]

[

ORDER BY

<column_reference> [ ASC | DESC ] [ NULLS FIRST | NULLS LAST ]

]

[

LIMIT <expression>

[

{ OFFSET | , }

<expression>

]

]

} | SCOPE_IDENTITY()

<expression> ::=

| <column_reference>

| @ <parameter>

| ?

| COUNT( * | { [ DISTINCT ] <expression> } )

| { AVG | MAX | MIN | SUM | COUNT } ( <expression> )

| NULLIF ( <expression> , <expression> )

| COALESCE ( <expression> , ... )

| CASE <expression>

WHEN { <expression> | <search_condition> } THEN { <expression> | NULL } [ ... ]

[ ELSE { <expression> | NULL } ]

END

| <literal>

| <sql_function>

<search_condition> ::=

{

<expression> { = | > | < | >= | <= | <> | != | LIKE | NOT LIKE | IN | NOT IN | IS NULL | IS NOT NULL | AND | OR | CONTAINS | BETWEEN } [ <expression> ]

} [ { AND | OR } ... ]

Examples

  1. Return all columns:

    SELECT * FROM Account

  2. Rename a column:

    SELECT [Name] AS MY_Name FROM Account

  3. Cast a column's data as a different data type:

    SELECT CAST(AnnualRevenue AS VARCHAR) AS Str_AnnualRevenue FROM Account

  4. Search data:

    SELECT * FROM Account WHERE FirstName <> 'Bob'

  5. The Amazon DynamoDB APIs support the following operators in the WHERE clause: =, !=, >, <, >=, <=, IS NULL, IS NOT NULL, CONTAINS, NOT CONTAINS, BETWEEN, IN, NOT IN, LIKE, NOT LIKE, AND, OR.

    SELECT * FROM Account WHERE FirstName <> 'Bob';

  6. Return the number of items matching the query criteria:

    SELECT COUNT(*) AS MyCount FROM Account

  7. Return the number of unique items matching the query criteria:

    SELECT COUNT(DISTINCT Name) FROM Account

  8. Return the unique items matching the query criteria:

    SELECT DISTINCT Name FROM Account

  9. Summarize data:

    SELECT Name, MAX(AnnualRevenue) FROM Account GROUP BY Name

    See Aggregate Functions below for details.

  10. Retrieve data from multiple tables.

    SELECT i.Amount, c.CustomerName FROM Invoices i, Customers c WHERE i.CustomerName = c.CustomerName

    See JOIN Queries below for details.

  11. Sort a result set in ascending order:

    SELECT Id, Name FROM Account ORDER BY Name ASC

  12. Restrict a result set to the specified number of rows:

    SELECT Id, Name FROM Account LIMIT 10

  13. Parameterize a query to pass in inputs at execution time. This enables you to create prepared statements and mitigate SQL injection attacks.

    SELECT * FROM Account WHERE FirstName = @param

Aggregate Functions

Examples of Aggregate Functions

Below are several examples of SQL aggregate functions. You can use these with a GROUP BY clause to aggregate rows based on the specified GROUP BY criterion. This can be a reporting tool.

COUNT

Returns the number of rows matching the query criteria.

SELECT COUNT(*) FROM Account WHERE FirstName <> 'Bob'

COUNT(DISTINCT)

Returns the number of distinct, non-null field values matching the query criteria.

SELECT COUNT(DISTINCT Id) AS DistinctValues FROM Account WHERE FirstName <> 'Bob'

COUNT

Returns the number of rows matching the query criteria.

SELECT COUNT(*) FROM Account WHERE FirstName = 'Bob'

COUNT(DISTINCT)

Returns the number of distinct, non-null field values matching the query criteria.

SELECT COUNT(DISTINCT Id) AS DistinctValues FROM Account WHERE FirstName <> 'Bob'

AVG

Returns the average of the column values.

SELECT Name, AVG(AnnualRevenue) FROM Account WHERE FirstName <> 'Bob' GROUP BY Name

MIN

Returns the minimum column value.

SELECT MIN(AnnualRevenue), Name FROM Account WHERE FirstName <> 'Bob' GROUP BY Name

MAX

Returns the maximum column value.

SELECT Name, MAX(AnnualRevenue) FROM Account WHERE FirstName <> 'Bob' GROUP BY Name

SUM

Returns the total sum of the column values.

SELECT SUM(AnnualRevenue) FROM Account WHERE FirstName = 'Bob'

JOIN Queries

The Provider for Amazon DynamoDB supports standard SQL joins like the following examples.

Inner Join

An inner join selects only rows from both tables that match the join condition:

SELECT i.Amount, c.CustomerName FROM Invoices i, Customers c WHERE i.CustomerName = c.CustomerName

Left Join

A left join selects all rows in the FROM table and only matching rows in the JOIN table:

SELECT i.Amount, c.CustomerName FROM Customers c LEFT JOIN Invoices i ON i.CustomerName = c.CustomerName

Date Literal Functions

The following date literal functions can be used to filter date fields using relative intervals. Note that while the <, >, and = operators are supported for these functions, <= and >= are not.

L_TODAY()

The current day.

SELECT * FROM MyTable WHERE MyDateField = L_TODAY()

L_YESTERDAY()

The previous day.

SELECT * FROM MyTable WHERE MyDateField = L_YESTERDAY()

L_TOMORROW()

The following day.

SELECT * FROM MyTable WHERE MyDateField = L_TOMORROW()

L_LAST_WEEK()

Every day in the preceding week.

SELECT * FROM MyTable WHERE MyDateField = L_LAST_WEEK()

L_THIS_WEEK()

Every day in the current week.

SELECT * FROM MyTable WHERE MyDateField = L_THIS_WEEK()

L_NEXT_WEEK()

Every day in the following week.

SELECT * FROM MyTable WHERE MyDateField = L_NEXT_WEEK()

Also available:

  • L_LAST/L_THIS/L_NEXT MONTH

  • L_LAST/L_THIS/L_NEXT QUARTER

  • L_LAST/L_THIS/L_NEXT YEAR

L_LAST_N_DAYS(n)

The previous n days, excluding the current day.

SELECT * FROM MyTable WHERE MyDateField = L_LAST_N_DAYS(3)

L_NEXT_N_DAYS(n)

The following n days, including the current day.

SELECT * FROM MyTable WHERE MyDateField = L_NEXT_N_DAYS(3)

Also available:

  • L_LAST/L_NEXT_90_DAYS

L_LAST_N_WEEKS(n)

Every day in every week, starting n weeks before current week, and ending in the previous week.

SELECT * FROM MyTable WHERE MyDateField = L_LAST_N_WEEKS(3)

L_NEXT_N_WEEKS(n)

Every day in every week, starting the following week, and ending n weeks in the future.

SELECT * FROM MyTable WHERE MyDateField = L_NEXT_N_WEEKS(3)

Also available:

  • L_LAST/L_NEXT_N_MONTHS(n)

  • L_LAST/L_NEXT_N_QUARTERS(n)

  • L_LAST/L_NEXT_N_YEARS(n)

Projection Functions

JSON_AVG(json, jsonpath)

Computes the average value of a JSON array within a JSON object.

  • json: The column containing JSON data.

  • jsonpath: The path to the json array.

JSON_COUNT(json, jsonpath)

Returns the number of elements in a JSON array within a JSON object.

  • json: The column containing JSON data.

  • jsonpath: The path to the json array.

JSON_MAX(json, jsonpath)

Gets the maximum value in a JSON array within a JSON object.

  • json: The column containing JSON data.

  • jsonpath: The path to the json array.

JSON_MIN(json, jsonpath)

Gets the minimum value in a JSON array within a JSON object.

  • json: The column containing JSON data.

  • jsonpath: The path to the json array.

JSON_SUM(json, jsonpath)

Computes the sum of the elements in a JSON within a JSON object.

  • json: The column containing JSON data.

  • jsonpath: The path to the json array.

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