Query specifications define requirements for items such as maximum number of tables in a "union" query.
| Item | Requirement | Notes |
|---|---|---|
|
Maximum number of tables participating in a query, for a query without a union, or for each side of a union in a query |
64 |
Maximum of 50 user tables, including result tables, tables referenced by views (the view itself is not counted) correlations and self-joins; maximum of 46 worktables |
|
Maximum number of tables in a “union” query |
256 |
Includes up to 50 user tables and 14 worktables on every side of the union, for a maximum of 256 tables across all sides of the union |
|
Maximum number of databases participating in one transaction |
Unlimited |
Includes database where transaction began, all databases changed during transaction, and tempdb, if it is used for results or worktables |
|
Practical number of databases participating in one query |
16 |
Includes each occurrence of each database queried and tempdb, if it is used for results or worktables |
|
Maximum number of tables with referential integrity constraints for a query |
192 |
|
| Number of items in an in clause. | Unlimited | No hardcoded limit, but potentially limited by free procedure cache. |