There are basically 4 techniques for this task, all of them standard SQL. NOT EXISTS Often fastest in Postgres. SELECT ip FROM login_log l WHERE NOT EXISTS ( SELECT — SELECT list mostly irrelevant; can just be empty in Postgres FROM ip_location WHERE ip = l.ip ); Also consider: What is easier to read in … Read more
Just in case anyone still cares: I had the same issue after copying a database directory directly using command cp -r /path/to/my/database /var/lib/mysql/new_database If you do this with a database that uses InnoDB tables, you will get this crazy ‘table does not exist’ error mentioned above. The issue is that you need the ib* files … Read more
The first is the most concise, I would go with that. The first two are the same, but the first is just that little bit shorter, so you’ll save on bytes. The third is plain wrong, because that condition will always evaluate true because the object will never be null or falsy for that matter.
Have a look at http://sqlite.org/lang_conflict.html. You want something like: insert or replace into Book (ID, Name, TypeID, Level, Seen) values ((select ID from Book where Name = “SearchName”), “SearchName”, …); Note that any field not in the insert list will be set to NULL if the row already exists in the table. This is why … Read more
SELECT SCHEMA_NAME FROM INFORMATION_SCHEMA.SCHEMATA WHERE SCHEMA_NAME = ‘DBName’ If you just need to know if a db exists so you won’t get an error when you try to create it, simply use (From here): CREATE DATABASE IF NOT EXISTS DBName;
You could also try EXISTS: SELECT EXISTS(SELECT * FROM table1 WHERE …) and per the documentation, you can SELECT anything. Traditionally, an EXISTS subquery starts with SELECT *, but it could begin with SELECT 5 or SELECT column1 or anything at all. MySQL ignores the SELECT list in such a subquery, so it makes no … Read more
The exists keyword can be used in that way, but really it’s intended as a way to avoid counting: –this statement needs to check the entire table select count(*) from [table] where … –this statement is true as soon as one match is found exists ( select * from [table] where … ) This is … Read more
You can use any: a_string = “A string is more than its parts!” matches = [“more”, “wholesome”, “milk”] if any(x in a_string for x in matches): Similarly to check if all the strings from the list are found, use all instead of any.
It seems some people are landing here, and simply want to know if an element exists (a little bit different to the original question). That’s as simple as using any of the browser’s selecting method, and checking it for a truthy value (generally). For example, if my element had an id of “find-me”, I could … Read more