如何在Codeigniter的查询生成器中使用select

Question

Given the following code:

$this->db->select();

the parameters in the select function are the names of the columns selected from the data base.

Suppose that one of the parameters inserted is: COUNT(column_name) .

Does it mean that only one row will be selected? (because COUNT returns a single value)

Answer 1

You can use like this:

$this->db->select('COUNT(column_name) AS Total, other_column_name');
$this->db->from('Table_name');

Answer 2

Does it mean that only one row will be selected ? (because COUNT returns a single value)

Of course yes, only one row will be selected, since the count is an aggregate operator, which makes only one row returned.

Please note using an aggregate function without a GROUP BY will always return one row, no matter what. You must use a GROUP BY if you want to return more than one row.

For more details read this