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Which is faster If I want to maintain a unique field in a table
Running a select query then insert query
OR directly running an insert query but have a unique field in the table instead
If you want to maintain a unique column in a database, then use the database mechanisms for that. Create a unique index or unique constraint on the column. Work with the database, not against it.
Furthermore, there is a major issue with your first approach. You are introducing a race condition. Two processes could attempt to insert the same record at the same time. They would both look at the values in the table and both would see that the insert is okay. And then both would insert the same value, creating a duplicate.
Of course, there are work-arounds for this, generally involving transactional logic or locking the tables. Both of these introduce additional overhead, which slows down performance.
Just create a unique column and don't worry about the uniqueness -- the database does the worrying for you.
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I must to make a decision if I split my table in more tables or I keep all in one table. According to my calculation if I will keep all in one table my table will have estimated 300.000 rows per year. Some people say to me to split table for every year. example 2019_table..
Some people say to split table in 4 tables(subcategories). I need an advice how to do it.
This is my current table https://ibb.co/jfZMKQJ
300K records is not really a large amount, and even over a decade, it is only 3 million records, which also is not very large. Assuming you can tune your database with appropriate indices, I don't see any reason to split into multiple tables. Even if you did have the need for this, you could try something like partitioning the table first (see the documentation).
300K records is not a large amount. Instead of splitting the tables, you better have to put an index on your datetime field assuming it is one of the fields you will use to filter your data.
See this answer for more details: Is it a good idea to index datetime field in mysql?
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Using MySQL, I want to retrieve all rows from a table A where a field contains "EQ" for example, copy them into table B (which has exactly the same field), and then delete them from table A.
I heard about triggers. Is that the right approach?
You need 2 SQL statements. First for inserting the data rows from A to B, and then for deleting those rows from A.
INSERT INTO B
SELECT *
FROM A
WHERE Field LIKE '%EQ%';
DELETE
FROM A
WHERE Field LIKE '%EQ%';
Triggers are a way to automate some activities when some other activity in a separate table happens. If you need to make sure that the above 2 operations should be triggered as soon someone INSERTS/DELETES/UPDATES on some other table, then you can create a trigger for that purpose. But with the simple requirement you gave above without any such dependency, I do not see a need of a trigger here.
If you do have such dependency and need, you have to provide proper requirements with details here.
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if I had a mysql table that has, lets say 300 million rows, how would I search for a row using
SELECT id WHERE coloumn = "abc" ;
most efficiently? Can I prepare the data so it would help the sql searching through the data? Or does it parse the rows row by row?
The SQL 101 answer here is an index using CREATE INDEX:
CREATE INDEX column_index ON table_name (`column_name`)
This of course depends on your schema. You can index more than one column as well and can apply UNIQUE constraints to ensure that each value is used only once.
On large tables the CREATE INDEX operation will be brutally slow to create the first time, so schedule some downtime if necessary. Once created it will be kept up-to-date automatically.
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I have two tables that should somehow be associated. Let's call them table_a and
table_b. A row in table_a can be associated with multiple rows in table_b, and the same goes the other way around. How could I achieve this? Should I use a pivot table?
Both tables have an auto-incrementing id-column.
What you're looking for is called a many-to-many relationship (a given user has zero or more games, a given game has zero or more users). This is typically handled with a "mapping table", e.g. USER_GAMES which has a user_id and a game_id, uniqueness is on the combination of these. http://www.joinfu.com/2005/12/managing-many-to-many-relationships-in-mysql-part-1/ has some good details.
As it is a many to many relationship, an intersection table with the user ID & game ID would be the best. Otherwise you would have to parse the list of game ID's stored in the user table and that would cause performance issues.
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I need to create mysql view with fulltext index. Are there way to create view in mysql with fulltext index.
Like table altering can I alter view to add full text index??
ALTER TABLE news ADD FULLTEXT(headline, story);
From the manual:
D.5 Restrictions on Views
View processing is not optimized:
It is not possible to create an index on a view.
Indexes can be used for views processed using the merge algorithm. However, a view that is processed with the temptable algorithm is unable to take advantage of indexes on its underlying tables (although indexes can be used during generation of the temporary tables).