SQL201

Sub Queries With Multiple Levels of Nesting

Let's go back to sub queries for a bit. You can nest a sub query within a sub query. There really is no limit. But in doing so, you really need to make sure

SQL201

Sub Query Fundamentals

Here we are with another sub query post. A sub query is a query that is nested inside a SELECT, INSERT, UPDATE, or DELETE statement, or inside another sub query

SQL201

The Error Message

When dealing with errors, it's often necessary to log, or pass on errors to your users. In either case, you've already seen how to trap the ERROR_NUMBER. This

SQL201

Correlated Subqueries in a HAVING Clause

Using sub queries in the HAVING clause is little different than using a sub query in any other part of the clause. The one thing that may through you is the

SQL102

UPDATE Triggers

Last time we discussed triggers, we covered insert triggers. This time we're doing UPDATE triggers. All the same rules apply to UPDATE triggers that apply to

t-sql

Correlated Subqueries with Comparison Operators

If you haven't used a sub query yet, I'm surprised. They can be incredibly useful. They can also be a crutch...but like I say time and again, each tool has it's

SQL201

Correlated Sub Queries with Aliases

I know I've covered sub queries before, but I wanted to make sure I made a specific point. When you create a correlated sub query, you can reference columns

SQL201

COUNT(*) vs COUNT(columnName)

Let's look at the following code using your copy of AdventureWorks. USE AdventureWorks GO SELECT COUNT(*) AS countStar , COUNT(ALL EmployeeID) AS

SQL201

Correlated Subqueries

The fundamental idea behind sub queries is you execute the sub query once, then take the value(s) from that sub query and substitute them in place of the sub

SQL201

Error Number

Every error generated in Microsoft SQL has a specific number, this number should uniquely identify the error that has occurred. This can be useful in building

t-sql

Insert Triggers

An insert trigger is a Data Manipulation Language (DML) trigger that acts when a new record is added to the table. CREATE TRIGGER t_tableName_insert ON

SQL102

SQL 102 – REVOKE

Like I mentioned previously REVOKE is like an undo function for GRANT and DENY. If you have a developer and you work with him for a while, you may find that