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SQL Server editions

SQL Server 2017 comes in 5 editions:

Enterprise	Unlimited virtualization, end to end business intelligence
Standard
Web	Targetting web hosters and Web VAP.
Developer	Includes all functionality of Enterprise edition, but is licenced for a development and test system only.
Express edition	entry level, free database. Ideal for learning or small applications

SQL Server Express LocalDB

Express edition comes also in a variant called SQL Server Express LocalDB which is a lightweight version of SQL Server Express.

Such an instance can be contacted with the service name(?) (localdb)\MSSQLLocalDb, for example with sqlcmd.exe:

C:\> sqlcmd -S (localdb)\MSSQLLocalDb