Difference Betwixt Cast, Convert, Together With Parse Component Subdivision Inward Microsoft Sql Server

Though all three, CAST, CONVERT as well as PARSE are used to convert ane information type into approximately other inward SQL Server, at that spot are approximately subtle differences betwixt them.The  CAST method accepts simply ii parameters, expression, as well as target type, but CONVERT() also takes a third parameter representing the format of conversion, which is supported for approximately conversions, similar betwixt graphic symbol strings as well as engagement fourth dimension values. For example, CONVERT(DATE, '2/7/2015', 101) converts the graphic symbol string '2/7/2015' to DATE using DATE format 101, representing the States standard. By using the PARSE function, y'all tin sack also betoken the civilisation past times using whatsoever civilisation supported past times the Microsoft's  dot NET framework. For example, PARSE('7/8/2015' AS DATE USING 'en-US') parse the input literal equally a DATE past times using a United State English linguistic communication Culture, similar to 101 formatting style.

CAST vs CONVERT vs PARSE inward MSSQL

Here are approximately other differences betwixt CAST, CONVERT as well as PARSE method for information type conversion inward SQL Server:

1) CAST is supported past times ANSI SQL Standard, hence it's a best exercise to prefer CAST over CONVERT as well as PARSE if its plenty to do the job.

2) PARSE component division relies on the presence of the .NET framework mutual linguistic communication runtime (CLR), which may live on an extra dependency as well as may non live on acquaint inward every Windows server where y'all receive got installed Microsoft SQL Server.


3) The PARSE component division supports an optional USING clause indicating the culture, which is whatsoever valid civilisation supported past times the .NET framework. If civilisation is non specified as well as hence it volition job the electrical current session's effective language.


4) Syntax
Using CAST:
CAST ( appear AS data_type )

Using CONVERT:
CONVERT ( data_type [ ( length ) ] , appear [ , mode ] )

Using PARSE
PARSE ( string_value AS data_type [ USING civilisation ] )  


Both CAST as well as CONVERT are used to explicitly converts an appear of dissimilar information types inward SQL

5) Examples
Let's run into approximately instance to convert DATE to VARCHAR inward Microsoft SQL Server using the cast(), convert(), as well as parse function.

CAST Function Example
Let's approximately instance of CAST component division to convert DATATIME information type to VARCHAR as well as  VARCHAR information type to SMALLINT information type inward SQL Server:

-- casting DATE to VARCHAR inward SQL Server SELECT CAST(GETDATE() AS VARCHAR(30)) AS Today  Today April 25 2017 6:32AM   -- CASTING VARCHAR to INT inward Microsoft SQL Server  SELECT CAST('1234' AS SMALLINT) AS Number Number 1234

You tin sack run into that the casting has been successful. If y'all desire to acquire to a greater extent than nearly CAST component division as well as how to convert all SQL Server information types e.g. numeric, money, datetime2 into VARCHAR as well as others, I propose y'all to reading Querying Microsoft SQL Server 2012, ane of the best books I receive got read inward SQL Server hence far. It is genuinely a written report guide of Microsoft SQL Server certification Exam 70-461 but at the same fourth dimension ane of the greatest majority to acquire T-SQL telephone substitution equally well.

CONVERT Function Example
Now, let's try to convert same values using Convert component division inward SQL Server:

-- converting DATE to VARCHAR inward SQL Server  SELECT CONVERT(VARCHAR(20), GETDATE(), 101) AS Today Today 07/23/2015  -- converting VARCHAR to INT inward Microsoft SQL Server SELECT Convert(bigint, '222222') AS MagicNumber MagicNumber 222222

Convert component division is mainly used to convert Date to VARCHAR value into dissimilar engagement format equally shown here.

Here is the hide shot of executing SQL queries alongside CAST as well as Convert inward SQL Server Management Studio:

PARSE Function Example
Let's run into approximately instance of PARSE component division to convert VARCHAR information type to DATETIME2 as well as MONEY information type using dissimilar locale or culture:

-- Parsing VARCHAR to DATETIME2 information type SELECT PARSE('Monday, 25 Dec 2017' AS datetime2 USING 'en-US') AS CurrentDate;   CurrentDate 2017-12-25 00:00:00.0000000  -- Parsing VARCHAR alongside currency symbol to MONEY information type SELECT PARSE('€345,98' AS money USING 'de-DE') AS Price;   Price 345.98

You tin sack run into that the sum of currency value Euro is parsed correctly because of High German culture, but if y'all try to alter the currency symbol to $ it volition non parse as well as reach y'all an mistake equally shown below:

-- Parsing VARCHAR alongside dollar currency symbol to MONEY information type using german culture SELECT PARSE('$345,98' AS money USING 'de-DE') AS Price;   Msg 9819, Level 16, State 1, Line 2 Error converting string value '$345,98' into information type money using civilisation 'de-DE'.

But equally before long equally y'all alter the civilisation to en-US it volition live on able to parse the currency value correctly, but do banking concern annotation downward the actual value which is real dissimilar from the german one, that's where a civilisation tin sack brand a large difference. 

-- Parsing VARCHAR alongside dollar currency symbol to MONEY information type using United States culture SELECT PARSE('$345,98' AS money USING 'en-US') AS Price;   Price 34598.00

Here is ane to a greater extent than instance of using PARSE component division inward SQL Server to parse String using implicit linguistic communication setting

-- PARSE alongside implicit setting of language -- The English linguistic communication language is mapped to en-US specific civilisation   SET LANGUAGE 'English';   SELECT PARSE('04/16/2017' AS datetime2) AS Output;    Output 2017-04-16 00:00:00.0000000

Here is the screenshot of executing PARSE related SQL queries on SSMS tool:

That's all nearly the difference betwixt CAST, CONVERT as well as PARSE inward SQL SERVER. Prefer CAST over CONVERT as well as PARSE because it's ANSI measure as well as your question volition live on to a greater extent than portable across different database vendors. I to a greater extent than frequently than non prefer CAST for casting betwixt VARCHAR as well as NUMERIC type, but I prefer to job CONVERT for converting String literals into DATE, TIME, as well as DATETIME types. I don't job PARSE, but is something expert to know nearly it.

Further Learning
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P.S.- If y'all are working inward Microsoft SQL Server 200, 2012 or 2014 version but doesn't experience real confident when using SQL Server as well as T-SQL specific features as well as functions as well as hence I propose y'all reading a expert majority on Microsoft SQL Server e.g. Microsoft SQL Server 2012 T-SQL Fundamentals (Developer Reference) 1st Edition past times Itzik Ben-Gan.. This is an first-class majority to foremost learning MSSQL database from scratch.