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sqlsql-serversql-server-2016select-query

select query without giving space in-between *(star) symbol

select*from tablename -- without spaces in-between the star symbol

select * from tablename -- Applied spaces in-between the star symbol

Both queries are working in my Sql-Server-2016 query window. What is the difference and which situation we need to use this? and why Sql server accept this?

Solution

  • There is no difference. As with many programming languages, T-SQL is parsed from input composed of strings. During parsing, many different types of "things" may be pulled from the text, such as KEYWORDs (such as select and from) and ASTERISK (*).

    It's simply the fact that there is no need for whitespace here since an asterisk character cannot be part of any KEYWORD or unescaped IDENTIFIER (such as a column or table name)1, and so there's no parsing ambiguity that whitespace would be required to help resolve.

    1It's not uncommon (cannot speak for T-SQL specifically) that the parser uses a single pattern just for IDENTIFIERs and a later step actually distinguishes IDENTIFIERs that are in a specifically enumerated list are in fact KEYWORDs.