SQL Server Tips: Temporary Tables, Constraints and Agent

These SQL Server tips cover temporary tables, declarative integrity and scheduled jobs. Each short tip needs a clear scope. The three examples below are followed by practical explanations.

Three SQL Server Tips

1. Avoid unnecessary use of temporary tables.
2. Prefer declarative constraints over triggers and rules whenever they can express the requirement.
3. SQL Server Agent allows you to schedule your own jobs and scripts.

Use temporary tables when their work is useful

The first tip says to avoid unnecessary temporary tables. A temporary table can hold an intermediate result that several later statements reuse. It can also provide a useful place to examine and index staged data.

Decide whether materializing the intermediate rows helps the actual workload. Compare the complete execution and reads, including the work required to populate that table.

Temporary-table prefixes identify their scope: local temporary tables start with #, and global temporary tables start with ##. An @ name denotes a variable, rather than a local temporary table.

Local temporary tables normally last until their creating session ends. A table created inside a stored procedure is normally dropped when that procedure finishes. Explicit cleanup can end its lifetime sooner.

With automatic global-table cleanup enabled, the creating session must end and other active references must finish. Disabling that option changes cleanup behavior. Do not use server restart as the ordinary cleanup method.

A temporary table does not automatically reduce server load. Creating and populating it costs work. Truncate-and-reload deduplication also needs a separate recovery, dependency and concurrency review.

Choose the integrity rule before its implementation

Use CHECK for an expressible domain rule and FOREIGN KEY for a supported relationship. PRIMARY KEY and UNIQUE express identity and uniqueness requirements. Choose the declarative rule that matches the requirement.

A default supplies a value when one is omitted. It does not reject every invalid supplied value. A trigger can address requirements that ordinary constraints cannot express, including some cross-table behavior.

Constraints, triggers, rules and defaults have different responsibilities. Prefer a suitable constraint for integrity, while retaining a default when its value-supply role is needed.

Schedule jobs with SQL Server Agent deliberately

SQL Server Agent runs configured jobs and can schedule their steps. Review the job owner, execution permissions, schedule, history and failure notification. A schedule alone does not prove that each run succeeded.

Check the installed product and edition before looking for Agent. SQL Server 2025 Express does not include it. An unavailable Agent service is different from a configured job that failed.

Learn the requirement behind each tip before applying it. When asking for clarification, include the query or job behavior you are investigating. The details make a short tip useful in a real situation.

A short tip is not a rule, it is a prompt to test your own workload.

Published by Pinal Dave on SQLAuthority. More of my work at pinaldave.com.