Merge pull request #65 from Azure-Samples/sqlextension

Adding the TO_CHAR function to the SQL Extension toolkit

Author: Matt Usher

SQL/Extension/Readme.md

@@ -31,6 +31,10 @@ The Azure Synapse SQL Extension will install a collection of vies to your Synaps
 
 ## Version History
 
+### December 1, 2020
+What's new:
+- [Function]: The `microsoft.to_char` script installs a function that emulates the `TO_CHAR(expression, format)` Teradata function.
+
 ### November 12th, 2020
 What's new:
 

SQL/Extension/deploy.bat

@@ -59,6 +59,7 @@ sqlcmd -S %_server% -d %_database% -U %_username% -P %_password% -I -i .\functio
 sqlcmd -S %_server% -d %_database% -U %_username% -P %_password% -I -i .\functions\microsoft.next_day.sql
 sqlcmd -S %_server% -d %_database% -U %_username% -P %_password% -I -i .\functions\microsoft.rpad.sql
 sqlcmd -S %_server% -d %_database% -U %_username% -P %_password% -I -i .\functions\microsoft.rtrim.sql
+sqlcmd -S %_server% -d %_database% -U %_username% -P %_password% -I -i .\functions\microsoft.to_char.sql
 
 ECHO Deploying views
 

SQL/Extension/functions/Readme.md

@@ -37,4 +37,7 @@ The `microsoft.next_day` script installs a function that emulates the `NEXT_DAY(
 The `microsoft.rpad` script installs a function that emulates the `RPAD(expression, length [, fill])` Teradata function.
 
 ## microsoft.rtrim
-The `microsoft.rtrim` script installs a function that emulates the `TRIM(TRAILING 'trim_characters' FROM expression)` Teradata function.
+The `microsoft.rtrim` script installs a function that emulates the `TRIM(TRAILING 'trim_characters' FROM expression)` Teradata function.
+
+## microsoft.to_char
+The `microsoft.to_char` script installs a function that emulates the `TO_CHAR(expression, format)` Teradata function.

SQL/Extension/functions/microsoft.to_char.sql

@@ -0,0 +1,74 @@
+IF EXISTS (SELECT * FROM sys.objects WHERE schema_id=SCHEMA_ID('microsoft') AND name = N'to_char')
+    DROP FUNCTION microsoft.to_char;
+GO
+
+CREATE FUNCTION microsoft.to_char(@date datetime2, @format VARCHAR(32) = '')
+RETURNS VARCHAR(128)
+WITH SCHEMABINDING
+AS
+BEGIN
+
+	-- Fast opt out
+	IF (@date IS NULL OR TRIM(@format) = '')
+		RETURN @date;
+
+	DECLARE @format_internal VARCHAR(48) = @format;
+	DECLARE @date_internal VARCHAR(256);
+
+	-- Special case for Day of Year (DDD or D3)
+	IF ( (CHARINDEX('DDD', @format_internal COLLATE Latin1_General_CS_AS) > 0) OR (CHARINDEX('D3', @format_internal COLLATE Latin1_General_CS_AS) > 0) )
+	  BEGIN
+		-- Ideally will support THROW here in a future Azure Synapse SQL release.
+		RETURN 'The format ''DDD'' (Day of Year) is not supported in T-SQL. Please try using the DATEPART(DAYOYYEAR, expression) syntax.'
+	  END
+
+	-- Special cases for hour separator
+	SET @format_internal = REPLACE(@format_internal COLLATE Latin1_General_CS_AS, 'h', '\h');
+
+	-- Special case for minute separator
+	SET @format_internal = REPLACE(@format_internal COLLATE Latin1_General_CS_AS, 'm', '\m');
+
+		-- Special case for second separator
+	SET @format_internal = REPLACE(@format_internal COLLATE Latin1_General_CS_AS, 's', '\s');
+
+	-- Replacements for year
+	SET @format_internal = REPLACE(@format_internal, 'YYYY', 'yyyy');
+	SET @format_internal = REPLACE(@format_internal, 'Y4', 'yyyy');
+	SET @format_internal = REPLACE(@format_internal, 'YY', 'yy');
+
+	-- Replacements for month
+	SET @format_internal = REPLACE(@format_internal, 'M4', 'MMMM');
+	SET @format_internal = REPLACE(@format_internal, 'M3', 'MMM');
+
+	-- Replacements for day
+	SET @format_internal = REPLACE(@format_internal, 'DD', 'dd');
+	SET @format_internal = REPLACE(@format_internal, 'D', 'd ');
+
+	-- Replacements for hour
+
+	-- Replacements for minute
+	SET @format_internal = REPLACE(@format_internal, 'MI', 'mm');
+
+	-- Replacements for 12/24 hour clock
+	SET @format_internal = REPLACE(@format_internal, 'T', 'tt');
+
+	-- Replacements for seconds
+	SET @format_internal = REPLACE(@format_internal, 'SS', 'ss');
+
+	-- Replacements for day of the week
+	SET @format_internal = REPLACE(@format_internal, 'EEEE', 'dddd');
+	SET @format_internal = REPLACE(@format_internal, 'E4', 'dddd');
+
+	SET @format_internal = REPLACE(@format_internal, 'EEE', 'ddd');
+	SET @format_internal = REPLACE(@format_internal, 'E3', 'ddd');
+
+	-- Replacements for separator B | b
+	SET @format_internal = REPLACE(@format_internal, 'B', ' ');
+	SET @format_internal = REPLACE(@format_internal, 'b', ' ');
+
+	SET @date_internal = FORMAT(@date, @format_internal);	
+
+	RETURN @date_internal;
+
+END
+GO