Question

I have a table, with lots of rows (more than 5,000,000,000), and I want to get the exact number of rows, but as the table has an atrribute called ID like:

    ID              someAtt someAtt2  someAtt3  
-----------------------------------------------  
    1               32      DOWN      45
    ...
    ...
    (lots of rows)
    ...
    ...   
    5,000,000,000   25      MOVE      40

What is it the best aproach to get the exact number (here 5,000,000,000)?
using max(ID) or SELECT COUNT(*) FROM table_name

Answer 1

Use COUNT(*). MAX(ID) will give you an inaccurate count if a row is ever deleted, while COUNT won’t. If you use COUNT(*) instead of a specific column name, the database server will decide on which column to use to optimize the operation.