How do you determine the cost of array operations and database operations?

PHP Database Data Array

If it is not particularly complicated operation, should query the database multiple times to get the data, or query the database at once, and then use the array concatenation operation is better? How do you decide which operation is more expensive? Thank you

Reply to discussion (solution)

The number of database queries must be less than the better.

If your database is a relational database such as MySQL, the bottleneck in the disk read and write Io, to minimize, because the PHP array operation is a memory operation, if it is Redis, MONGO and so on itself is the memory caching mechanism of the database does not matter.

This depends on what the database is, different database processing methods are different.

If your database is a relational database such as MySQL, the bottleneck in the disk read and write Io, to minimize, because the PHP array operation is a memory operation, if it is Redis, MONGO and so on itself is the memory caching mechanism of the database does not matter.

is not PHP inside useless to IO operation is memory operation? How do you distinguish it from little white?

PHP function Operation memory operation, MySQL read IO operation.

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