CODEWITHSUNDEEP
mysqlsql
user1599078
user1599078

Reputation: 167

Mysql avoid duplicate URLS

Is there an SQL statement to check if a field exists? Example: I have a database with the following: URL, IsCrawled, Level Etc. I need to check to see if the URL is already there. I do not care about the other fields. I am writing a very fast crawler, and this is needed.

Upvotes: 2

Views: 250

Answers (3)

Erre Efe
Erre Efe

Reputation: 15557

Why don't you use a plain select under any index:

SELECT ID FROM TABLE WHERE URL = @URL

If the select isn't null then there's already one.

Now, another better idea depending on your problem would be to add a UNIQUE CONSTRAINT so by design your DB will not allow duplicates of that value.

Now, going a little forward if you want to compare only part of the URL to see (ie the domain) then you can use the LIKE comparison function to see if there's already one URL stored with the same domain name.

Upvotes: 1

John Woo
John Woo

Reputation: 263723

Is this what you want?

SELECT COUNT(*)
FROM tableName
WHERE `URL` = 'urlHERE'

It will have a result of 0 if it doesn't exists. Or add a unique index on the fieldd URL

ALTER TABLE tableName
ADD CONSTRAINT indexName UNIQUE (`Url`)

in this way, the Insert statement will fail if you insert a url which already exists.

Upvotes: 1

hjpotter92
hjpotter92

Reputation: 80639

ALTER TABLE `table`
ADD UNIQUE INDEX `urls` (`URL`)

or simple,

ALTER TABLE `table`
ADD UNIQUE(`URL`);

Though, I use the first method. Have only read about the second method to work too. It may not be so.

Upvotes: 3

Related Questions