Xero

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 Contacts
2. Rename a column:

   SELECT [Name] AS MY_Name FROM Contacts
3. Cast a column's data as a different data type:

   SELECT CAST(Discount AS VARCHAR) AS Str_Discount FROM Contacts
4. Search data:

   SELECT * FROM Contacts WHERE ContactStatus = 'ACTIVE'
5. Return the number of items matching the query criteria:

   SELECT COUNT(*) AS MyCount FROM Contacts
6. Return the number of unique items matching the query criteria:

   SELECT COUNT(DISTINCT Name) FROM Contacts
7. Return the unique items matching the query criteria:

   SELECT DISTINCT Name FROM Contacts
8. Summarize data:

   SELECT Name, MAX(Discount) FROM Contacts GROUP BY Name

   See Aggregate Functions below for details.

9. Retrieve data from multiple tables.

   SELECT a.Name, po.Total FROM Contacts a, PurchaseOrders po WHERE a.ContactId = po.Contact_ContactlId

   See JOIN Queries below for details.

10. Sort a result set in ascending order:

    SELECT Discount, Name FROM Contacts ORDER BY Name ASC
11. Restrict a result set to the specified number of rows:

    SELECT Discount, Name FROM Contacts LIMIT 10
12. Parameterize a query to pass in inputs at execution time. This enables you to create prepared statements and mitigate SQL injection attacks.

    SELECT * FROM Contacts WHERE ContactStatus = @param

Aggregate Functions

COUNT

Returns the number of rows matching the query criteria.

SELECT COUNT(*) FROM Contacts WHERE ContactStatus = 'ACTIVE'

COUNT(DISTINCT)

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

SELECT COUNT(DISTINCT Discount) AS DistinctValues FROM Contacts WHERE ContactStatus = 'ACTIVE'

AVG

Returns the average of the column values.

SELECT Name, AVG(Discount) FROM Contacts WHERE ContactStatus = 'ACTIVE' GROUP BY Name

MIN

Returns the minimum column value.

SELECT MIN(Discount), Name FROM Contacts WHERE ContactStatus = 'ACTIVE' GROUP BY Name

MAX

Returns the maximum column value.

SELECT Name, MAX(Discount) FROM Contacts WHERE ContactStatus = 'ACTIVE' GROUP BY Name

SUM

Returns the total sum of the column values.

JOIN Queries

The Provider for Xero 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 a.Name, po.Total FROM Contacts a, PurchaseOrders po WHERE a.ContactId = po.Contact_ContactlId

Left Join

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

SELECT c.Name, po.Total FROM Contacts c LEFT JOIN PurchaseOrders po ON c.ContactId = po.Contact_ContactId

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)