What do these curly braces mean? - sql

Question

I am working through a rails tutorial, and came across this line rails g model product name decimal:{7, 2}.
What do those curly braces at the end mean? What do they do?
Originally, I thought they force a level of precision with floating point numbers, but that proved to be false. I could make a decimal 10 digits long with a decimal going to the thousandths place.

Answer 1

Please see for example:
- http://api.rubyonrails.org/classes/ActiveRecord/ConnectionAdapters/TableDefinition.html
There it says:
For clarity’s sake: the precision is the number of significant digits,
while the scale is the number of digits that can be stored following
the decimal point. For example, the number 123.45 has a precision of 5
and a scale of 2. A decimal with a precision of 5 and a scale of 2 can
range from -999.99 to 999.99.

Answer 2

It's the decimal field's precision (total number of digits) and scale (digits after the decimal point).
From rails g model -h:
For decimal two integers separated by a comma in curly braces will be used
for precision and scale:
`rails generate model product price:decimal{10,2}`
From MySQL docs:
The declaration syntax for a DECIMAL column is DECIMAL(M,D). The
ranges of values for the arguments in MySQL 5.1 are as follows:
M is the maximum number of digits (the precision). It has a range of 1
to 65. (Older versions of MySQL permitted a range of 1 to 254.)
D is the number of digits to the right of the decimal point (the
scale). It has a range of 0 to 30 and must be no larger than M.