问题
I have to put the price of some items inside a mysql table. When creating the table I'm using DECIMAL(10,2) as I don't need more than 2 digits after the comma (for example: 123,45 would be accepted as an input but 123,456 would be rounded to 123,45 with PHP).
First question: using DECIMAL(10,2), how do I know how many numbers may be stored before the comma? I know it is not 10, as 10 is just the precision Mysql uses when doing math with those numbers: so where the length of the number itself is specified?
Second question: I'm using PHP to round user input to fit the data type (float with 2 numbers after the comma). How should I use mysqli->bind_param to insert those data? Which of these datatypes (from the documentation) accepted by bind_param should I use (and possibly: why)?
Character Description
i corresponding variable has type integer
d corresponding variable has type double
s corresponding variable has type string
b corresponding variable is a blob and will be sent in packets
回答1:
DECIMAL(10,2) means that 10 is the maximum number of digits to be used. The 2 specifies that there are two on the right side of the decimal. So this means there are 8 digits left on the left side. See the manual
As for the datatype, you should use double as this is for decimal numbers.
Integer has no decimal chars, so it will floor all numbers. String is for text and not numeric values. Blob is for a binary large object, EG: an image
来源：https://stackoverflow.com/questions/16940263/handle-decimal-numbers-in-mysqli