SQL Statement Meaning - sql

Question

Can someone tell me what this SQL statement is doing? Break it down as to what each part of the statement is doing.
convert(char(11),(field name 1 + right('0' + cast(field name 2 as varchar(2),2))

Answer 1

convert(char(11),(field_name_1 + right('0' + cast(field_name_2 as varchar(2),2))
convert() (documentation https://technet.microsoft.com/en-us/library/ms187928(v=sql.105).aspx):
Tells the sql server to convert the value in the second parameter to the type given in the first parameter.
char(11):
Tells the sql server that the value behind the command needs to become a character field type, of a maximum length of 11 characters.
after the comma we have the following
(field_name_1 + right('0' + cast(field_name_2 as varchar(2),2)
field_name_1 corresponds to the field on the table you're reading. It will get the value of that field and put it there.
+ means append string. Append the value that follows after the + to the value before the +
for example
'foo' + 'bar' = 'foobar'
'foo' + 'baz = 'foobaz'
So in this case whatever follows behind the + should be appended tot he value of field_name_1
right is a function, get N characters starting from the end of the string(documentation https://learn.microsoft.com/en-us/sql/t-sql/functions/right-transact-sql)
within this function a lot happens. But the first part before the comma '0' + cast(field_name_2 as varchar(2) is the string right is called upon, and the 2 is the number of characters to select from it, starting from the end.
So if you have the following values fed into right
013
03
044
you'll end up with
13
03
44
Now we have this part:
'0' + cast(field_name_2 as varchar(2)`
'0' is a string literal. This is just a string, of length one, that contains the character 0
+ means append string. Append the value that follows after the + to the value before the +
So in this case, anything that follows the + will be appended to 0.
example:
'0' + 'foo' = '0foo'
'0' + '1' = '01'
cast(field_name_2 as varchar(2))
In your code you're actually missing a closing ) here, might cause you some trouble.
Basically what it does it takes the value of field_name_2 which is probably of the type integer(just guessing) and converts it to the type of varchar, with a maximum length of 2(guessing the number will never exceed 99).
so a number with value of 1 gets turned into a string with the character for the value 1, namely '1'.
2 = '2';
33 = '33';
42 = '42';
this combined with the previous part would yield
'0' + '2' = '02';
'0' + '33' = '033';
'0' + '42' = '042';
that will be fed into the right(value, 2); which will result in
right('02', 2) = '02';
right('033', 2) = '33';
right('042', 2) = '42';
which will be appended to the value of field_name_1
'foobar' + '02' = 'foobar02';
which is then converted in a character type string value of maximum 11 characters long.