Function Calls

Quince defines C++ functions that wrap certain SQL functions; i.e. they build and return exprn_mappers that represent SQL function calls.

E.g., if str is some abstract_mapper<std::string>, then length(str) builds an exprn_mapper<int32_t> which, when executed, evaluates the SQL subexpression represented by str, and passes the result to the SQL length function.

Here is a list of all the quince functions that wrap SQL functions in this way:

Quince function name	Argument is `abstract_mapper<`...`>`	Returns `exprn_mapper<`...`>`	SQL function name
`abs`	`int16_t`	`int16_t`	`abs`
`abs`	`int32_t`	`int32_t`	`abs`
`abs`	`int64_t`	`int64_t`	`abs`
`abs`	`float`	`float`	`abs`
`abs`	`double`	`double`	`abs`
`lower`	`std::string`	`std::string`	`lower`
`upper`	`std::string`	`std::string`	`upper`
`length`	`std::string`	`int32_t`	`length`
`avg`	`int16_t`	`boost::optional<double>`	`avg`
`avg`	`int32_t`	`boost::optional<double>`	`avg`
`avg`	`int64_t`	`boost::optional<double>`	`avg`
`avg`	`float`	`boost::optional<double>`	`avg`
`avg`	`double`	`boost::optional<double>`	`avg`
`count`	any type	`int64_t`	`count`
`sum`	`int16_t`	`int64_t`	`sum`
`sum`	`int32_t`	`int64_t`	`sum`
`sum`	`int64_t`	`int64_t`	`sum`
`sum`	`float`	`double`	`sum`
`sum`	`double`	`double`	`sum`
`max`	any single-column type `T`	`boost::optional<``T``>`	`max`
`min`	any single-column type `T`	`boost::optional<``T``>`	`min`

Function constants

Quince defines two function constants:

count_all is an exprn_mapper<int64_t> that wraps SQL's COUNT(*)
empty is a predicate (i.e. an exprn_mapper<bool>). It is defined as count_all==int64_t(0).

E.g.:

const query<int64_t> n_points = points.select(count_all);
const query<bool> no_points = points.select(empty);

As we shall see, quince provides special means of creating and executing queries that end in .select(count_all) or .select(empty).

Function Calls

Pre-wrapped functions

Function constants