Merge pull request #72 from Azure-Samples/sqlextension

Adding the DATE_TRUNC function

Author: Matt Usher

SQL/Extension/Readme.md

@@ -38,6 +38,7 @@ The Azure Synapse SQL Extension will install a collection of vies to your Synaps
 
 ### December 15, 2020
 What's new:
+- [Function]: The `microsoft.date_trunc` script installs a function that emulates the `DATE_TRUNC(date_part, expression)` IBM Netezza function.
 - [Function]: The `microsoft.firstdayofmonth` script installs a function that returns the first day of the specified month as DATETIME2.
 - [Function]: The `microsoft.firstdayofquarter` script installs a function that returns the first day of the specified quarter as DATETIME2.
 - [Function]: The `microsoft.firstdayofyear` script installs a function that returns the first day of the specified year as DATETIME2.

SQL/Extension/clean.sql

@@ -1,22 +1,9 @@
-/*SELECT
-	'IF EXISTS (SELECT * FROM sys.objects WHERE schema_id=SCHEMA_ID('''+ SCHEMA_NAME(schema_id) +''') AND name = N'''+ name +''') DROP ' + 
-	CASE type
-		WHEN 'FN' THEN 'FUNCTION'
-		WHEN 'V' THEN 'VIEW'
-	END + ' [' + SCHEMA_NAME(schema_id) + '].[' + name + '];'
-FROM
-	sys.objects
-ORDER BY
-	type,
-	schema_id,
-	name;
-	*/
-
 -- Functions
 PRINT 'Removing functions';
 IF EXISTS (SELECT * FROM sys.objects WHERE schema_id=SCHEMA_ID('microsoft') AND name = N'acosh') DROP FUNCTION [microsoft].[acosh];
 IF EXISTS (SELECT * FROM sys.objects WHERE schema_id=SCHEMA_ID('microsoft') AND name = N'asinh') DROP FUNCTION [microsoft].[asinh];
 IF EXISTS (SELECT * FROM sys.objects WHERE schema_id=SCHEMA_ID('microsoft') AND name = N'btrim') DROP FUNCTION [microsoft].[btrim];
+IF EXISTS (SELECT * FROM sys.objects WHERE schema_id=SCHEMA_ID('microsoft') AND name = N'date_trunc') DROP FUNCTION [microsoft].[date_trunc];
 IF EXISTS (SELECT * FROM sys.objects WHERE schema_id=SCHEMA_ID('microsoft') AND name = N'dayoccurrence_of_month') DROP FUNCTION [microsoft].[dayoccurrence_of_month];
 IF EXISTS (SELECT * FROM sys.objects WHERE schema_id=SCHEMA_ID('microsoft') AND name = N'firstdayofmonth') DROP FUNCTION [microsoft].[firstdayofmonth];
 IF EXISTS (SELECT * FROM sys.objects WHERE schema_id=SCHEMA_ID('microsoft') AND name = N'firstdayofquarter') DROP FUNCTION [microsoft].[firstdayofquarter];

SQL/Extension/deploy.bat

@@ -48,6 +48,7 @@ ECHO Deploying functions
 REM Functions
 sqlcmd -S %_server% -d %_database% -U %_username% -P %_password% -I -i .\functions\microsoft.acosh.sql
 sqlcmd -S %_server% -d %_database% -U %_username% -P %_password% -I -i .\functions\microsoft.asinh.sql
+sqlcmd -S %_server% -d %_database% -U %_username% -P %_password% -I -i .\functions\microsoft.date_trunc.sql
 sqlcmd -S %_server% -d %_database% -U %_username% -P %_password% -I -i .\functions\microsoft.dayoccurrence_of_month.sql
 sqlcmd -S %_server% -d %_database% -U %_username% -P %_password% -I -i .\functions\microsoft.firstdayofmonth.sql
 sqlcmd -S %_server% -d %_database% -U %_username% -P %_password% -I -i .\functions\microsoft.firstdayofquarter.sql

SQL/Extension/functions/Readme.md

@@ -9,6 +9,9 @@ The `microsoft.asinh` script installs a function that emulates the `ASINH(expres
 ## microsoft.btrim
 The `microsoft.btrim` script installs a function that emulates the `TRIM(BOTH 'trim_characters' FROM expression)` Teradata function.
 
+## microsoft.date_trunc
+The `microsoft.date_trunc` script installs a function that emulates the `DATE_TRUNC(date_part, expression)` IBM Netezza function.
+
 ## microsoft.dayoccurrence_of_month
 The `microsoft.dayoccurrence_of_month` script installs a function that emulates the `DAYOCCURRENCE_OF_MONTH(expression)` Teradata function.
 

SQL/Extension/functions/microsoft.date_trunc.sql

@@ -0,0 +1,64 @@
+IF EXISTS (SELECT * FROM sys.objects WHERE schema_id=SCHEMA_ID('microsoft') AND name = N'date_trunc')
+    DROP FUNCTION microsoft.date_trunc;
+GO
+
+/*
+Note: The DATEDIFF function returns a 4-byte integer (int). Until Azure Synapse SQL supports DATEDIFF_BIG 
+	  with an 8-byte integer return type, date_trunc can and likely will throw an overflow exception when
+	  truncating small date_part units like second or smaller.
+*/
+
+CREATE FUNCTION microsoft.date_trunc(@unit VARCHAR(15), @expression VARCHAR(8000))
+RETURNS DATETIME2
+WITH SCHEMABINDING
+AS
+BEGIN
+
+	-- Declarations
+	DECLARE @result DATETIME2;
+
+	SET @unit = UPPER(@unit);
+
+	SET
+		@result = 
+		(
+			CASE
+				-- Year
+				WHEN @unit = 'Y' OR @unit = 'YEAR' THEN DATEADD(YEAR, DATEDIFF(YEAR, 0, @expression), 0) 
+
+				-- Month
+				WHEN @unit = 'M' OR @unit = 'MONTH' THEN DATEADD(MONTH, DATEDIFF(MONTH, 0, @expression), 0) 
+
+				-- Day
+				WHEN @unit = 'D' OR @unit = 'DAY' THEN DATEADD(DAY, DATEDIFF(DAY, 0, @expression), 0) 
+
+				-- Hour
+				WHEN @unit = 'H' OR @unit = 'HOUR' THEN DATEADD(HOUR, DATEDIFF(HOUR, 0, @expression), 0) 
+
+				-- Minute
+				WHEN @unit = 'MINUTE' THEN DATEADD(MINUTE, DATEDIFF(MINUTE, 0, @expression), 0) 
+
+				-- Second
+				WHEN @unit = 'S' OR @unit = 'SECOND' THEN DATEADD(SECOND, DATEDIFF(SECOND, 0, @expression), 0) 
+
+				-- Millisecond 
+				WHEN @unit = 'MS' OR @unit = 'MILLISECOND' THEN DATEADD(MILLISECOND, DATEDIFF(MILLISECOND, 0, @expression), 0) 
+
+				-- Microsecond 
+				WHEN @unit = 'MICROSECOND' THEN DATEADD(MICROSECOND, DATEDIFF(MICROSECOND, 0, @expression), 0) 
+
+				-- Nanosecond 
+				WHEN @unit = 'NANOSECOND' THEN DATEADD(NANOSECOND, DATEDIFF(NANOSECOND, 0, @expression), 0) 
+
+				-- Week
+				WHEN @unit = 'W' OR @unit = 'WEEK' THEN DATEADD(DAY, -(DATEPART(WEEKDAY, @expression) - 1), @expression)
+
+				-- Quarter
+				WHEN @unit = 'QUARTER' THEN microsoft.FirstDayOfQuarter(@expression)
+			END
+		);
+
+	RETURN @result;
+
+END
+GO