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Macros > LispMacros > ManageSGFRecords > ManifestTyping > MarkUp > MartinFowler > Maven > McCarthy > Memex > MemoryLeaks > MercurialHosting > Merging > MetaOCaml > OCaml > MichaelFeathers > MicroFormats > MicrosoftSQLServerClear Trailit causes all statements from the beginning of the script or the last GO statement (whichever is closer) to be compiled into one execution plan and sent to the server independent of any other batches[1]
A batch is a set of Transact-SQL statements that are submitted together and executed as a group. Use a GO statement in SQL Query Analyzer and the osql utility to signal the end of a batch. The scope of user-defined variables is limited to a batch.[2]
There are no significant differences between creating a UNIQUE constraint and creating a unique index independent of a constraint. Data validation occurs in the same manner and the query optimizer does not differentiate between a unique index created by a constraint or manually created. However, you should create a UNIQUE or PRIMARY KEY constraint on the column when data integrity is the objective. By doing this the objective of the index will be clear.[3]
A constraint is an abstract concept, an index is an implementation detail.
An index is a physical construct, a constraint is a logical construct. ANSI SQL supports constraints but doesn't care about physical implementation so doesn't address anything with indexes.