Joins And Parentheses

Kevin Feasel

2017-12-08

T-SQL

Shane O’Neill walks through different ways of grouping tables in a SQL query:

Asker: that’d be awesome if i can inner join two other tables instead of the table mentioned after FROM keyword
Me: …wait, what?
A: He’s asking
t1 left join t12
t1 left join t13
t12 inner join t13
M: em…it’s possible but it’s…iffy
A:  i wanna learn it.
do your magic

I’ve seen this in action before, but rewrote the queries not to do this.  The problem is that as the query gets more complicated, it becomes much harder to diagram things mentally.  I don’t think I’ve seen a use yet that I couldn’t rewrite to be simpler.

Related Posts

Recently Added String Functions

Lori Brown covers a few string functions added to SQL Server in the past two versions: STRING_ESCAPE (https://docs.microsoft.com/en-us/sql/t-sql/functions/string-escape-transact-sql) This function is available starting with SQL 2016 and is currently only able to escape JSON characters. To me it’s not super useful just yet but hopefully they will add more types soon. 1 SELECT STRING_ESCAPE(‘SQLRX’‘s beginning was […]

Read More

Finding Overlapping Data Ranges

Louis Davidson shows how to find groups of data which overlap: This week, I had a problem where I needed to find and eliminate from the results of my query, data with overlapping ranges. I have written about this topic before, in my database design book book, in regards to building a trigger to avoid overlapping […]

Read More

Categories

December 2017
MTWTFSS
« Nov Jan »
 123
45678910
11121314151617
18192021222324
25262728293031