Module: SQLHelpers

Extended by:
SQLHelpers
Included in:
SQLHelpers
Defined in:
lib/sql/statement.rb,
lib/sql/expression.rb

Instance Method Summary collapse

Instance Method Details

#sql_func(&block) ⇒ Object

this function takes a block containing an expression, and converts it to a proper SQL expression.

The rules for doing so are quite complex:

  • all Ruby binary operaters are converted to their SQL equivalents

  • the + operator on strings is never converted to the

<tt>concat()</tt> function. Use the concat() function directly.

  • the count_distinct(...) function is converted to

<tt>count(distinct ...)</tt>.

  • all Ruby variable references are evaluated and their values

substituted, with the exception of the special +sql+ logical
method reciever.

  • method calls on ruby objects are evaluated, with the exception of

the logical +sql+ method reciever.

  • free functions (for example count(:field)) that are

undefined in the surrounding scope are returned as SQL
function calls.

  • free functions that are defined in the surrounding scope are

called by Ruby. To override this behavior, specify the function
as a method call on the virtual reciever +sql+ (for example,
<tt>sql.object_id</tt> becomes <tt>object_id()</tt>, because
in ordinary Ruby contexts, object_id is almost always defined,
and will therefore be evaluated.)

  • Symbols are interpreted as field names, just like everywhere else 

in this library. Array indexes evaluate to tablename.fieldname
references. The special symbol <tt>:*</tt> converts to a literal 
SQL <tt>*</tt>

  • #{...} interpolated strings are not supported (yet).

  • Other objects (except Arrays) are treated as themselves.



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# File 'lib/sql/expression.rb', line 60

def sql_func(&block)
   sxp(&block)
end

#string_func(str, placeheld = []) ⇒ Object

This helper method takes a string, and encapsulates it as a proper SQL expression, so that it won’t get passed to the database as though it were a (potentially hostile) string value.



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# File 'lib/sql/statement.rb', line 58

def string_func(str,placeheld=[])
   SQLStatement::Function.new(str,placeheld)
end