SQL201

SQL201

Variables And Parameters

Transact SQL (T-SQL) has two main wait of passing data, variables, and parameters. A variable is an object in T-SQL batches and scripts that can old a value.

SQL201

Flow Control

When you want to build more intelligent or more flexible T-SQL scripts, you're going to need to know how to control the flow of the program. You'll need the

SQL201

The Error Severity

Errors can have different levels of severity. Based on this severity, you may wish to handle the error in different ways (see my articles on TRY..CATCH). In

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

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