How Union better(WHERE or JOIN)?
Scheme:
Association with a JOIN:
Code:
Join using WHERE clause:
Code:
They output the same thing. Which query is better to use for such purposes?
Association with a JOIN:
Code:
SELECT Wizards.Name AS the Master Services.Name AS Name,
Services.The cost AS Cost, Services.Polovians AS [Gender]
FROM Services
INNER JOIN (Wizards
INNER JOIN Masterplug
ON the Masters.Codemaster=Masterplug.Codemaster)
ON Services.Codului=Masterplug.Codului;Join using WHERE clause:
Code:
SELECT Wizards.Name AS the Master Services.Name AS Name,
Services.The cost AS Cost, Services.Polovians AS [Gender]
FROM the Masters, Services, Masterplug
WHERE Wizards.Codemaster = Masterplug.Codemaster
AND Services.Codului = Masterplug.Codului;They output the same thing. Which query is better to use for such purposes?
asked July 9th 19 at 10:19
2 answers
answered on
Solution
So many tags of different databases, each database has its own profiling tools, run both queries through them. If both queries run equally fast, then the best option that is more friendly and pleasant.
answered on July 9th 19 at 10:23
The first option is not very good, that contains a subquery, and this additional execution time.
The version with commas is quite right to existence, but, in my opinion, is not very convenient to read.
I would write something like this
The version with commas is quite right to existence, but, in my opinion, is not very convenient to read.
I would write something like this
SELECT Wizards.Name AS the Master Services.Name AS Name, Services.The cost AS Cost, Services.Polovians AS [Gender]
FROM Masterplug
INNER JOIN Wizards
ON the Masters.Codemaster = Masterplug.Codemaster
INNER JOIN Services
ON Services.Codului = Masterplug.CoduluiI may surprise you, but sometimes subqueries work faster joynow. Therefore, only the profiling. commented on July 9th 19 at 10:26
In General, I agree, especially since the tags in different databases, it is necessary to look. In particular, the 3 dB mostly worked with ms sql and subqueries are usually caused brakes. commented on July 9th 19 at 10:29
Everything depends on the particular optimizer queries, and a set of data. And not the fact that after the change of the structure of the tables will still work well. commented on July 9th 19 at 10:32
Find more questions by tags Microsoft AccessSQL ServerMySQLSQL
Additionally, the speed can raise a competent use of the indexes. - scottie.Walk commented on July 9th 19 at 10:24