What does # indicate in MSSQL SELECT FROM?-CodePudding

Can someone quickly explain to me (as in without directing me to an illegible mountain of documentation) what a construct such as this (below) means in an MSSQL stored procedure.

Note, this is in a stored procedure on a database which resides on a server with many other databases and this is a generalization not the exact query

INSER INTO [schema].TableName
(
  Field1,
  Field2
)
SELECT
  OtherField1,
  OtherField2
FROM #Something TMP
  INNER JOIN [schema].[Field] A
    ON A.Whatever = TMP.Whatever;

Note: I've been using MySQL and Postgres for years so understand the basics, but this MSSQL has a lot of features that are new to me. What I can tell here is that we are filling a table with the results from another table (or something) and that is what i want to know. What is the or something? in this example, what does "#Something" actually reference?

I am aware of Linked servers, but i don't see one in this system with the name referenced. And i also don't see any definition in this stored procedure of what #Something references.

One thought I had was that perhaps a stored procedure can use another stored procedure and in that way perhaps this #Something is defined in the calling procedure? is this even possible?

CodePudding user response：

Object names that start with a # are temporary objects. A single # means that the object is limited to the local scope (so therefore must have been created in the same scope of a parent of it), and 2 (or more) #s at the start denote "global" temporary objects, where they can be referenced in any scope.

Either way, a temporary object is dropped once the scope that created it ends or the object is no longer in use (which ever is last).

CodePudding user response：

This indicates that the table in question is a temp table.

You can find the table by checking the system database.
SELECT * FROM tempdb.sys.table WHERE name LIKE '#something%'