具有多列或单列的MySQL数据库设计

Question

Hi just a simple question
I need to store data to database, there are 2 option to show now

Data : a,b,c,d
1. store a,b,c,d in 1 column, when needed only query and perform splitting in application
2. store a,b,c,d to 4 different column, can query directly from database

Which option will be better? My concern is split it into 4 different column will make the tables contain many column, does it slow down the performance? And also I am curious is it possible the query is fast but the transfer of data to my application is slow?

Answer 1

MySQL performance is a complicated subject. To the issue you raised:

My concern is split it into 4 different column will make the tables contain many column, does it slow down the performance?

there is nothing inherently worse, from a performance perspective, to have 4 columns, or 10, or 20, or 50.

Now, that being said, there are things that could impact performance, and probably will if you don't know about them. For example, if you SELECT * FROM {my_table} when really you only need to SELECT a FROM {my_table} ... yeah, that'll impact your performance (although there are arguments to be made in favor of SELECT * FROM {my_table} depending on your caching strategy).

Likewise, you'll want to consider LIMIT statements. To your question

And also I am curious is it possible the query is fast but the transfer of data to my application is slow?

Yes, of course. If you only need 50 rows and your table has 50000, you're gonna want to add limit clauses to your SQL statements, or you'll be sending a lot more data over the wire than you need to be. Memory is faster than disk and disk is faster than network. If you're sending a lot of data over the wire that you don't need, you better believe it's gonna cause performance problems. But again, keep in mind, that has nothing to do with how many columns you have. There is absolutely nothing inherent in the number of columns a table has that affects performance (at least not at the scale that you're talking about and in the way that you are thinking about it)

All of which to say, performance is a complex topic. You should take a look into it, if you're interested. And it sounds like a,b,c, and d are logically different columns, so you should probably go ahead and store them in different columns in MySQL. Hope this helps.