| Stability | experimental |
|---|---|
| Maintainer | Leon P Smith <leon@melding-monads.com> |
| Safe Haskell | None |
Database.PostgreSQL.Simple.SqlQQ
Description
- sql :: QuasiQuoter
Documentation
sql :: QuasiQuoter
sql is a quasiquoter that eases the syntactic burden
of writing big sql statements in Haskell source code. For example:
{-# LANGUAGE QuasiQuotes #-}
query conn [sql| SELECT column_a, column_b
FROM table1 NATURAL JOIN table2
WHERE ? <= time AND time < ?
AND name LIKE ?
ORDER BY size DESC
LIMIT 100 |]
(beginTime,endTime,string)
This quasiquoter attempts to mimimize whitespace; otherwise the above query would consist of approximately half whitespace when sent to the database backend. It also recognizes and strips out standard sql comments --.
The implementation of the whitespace reducer is currently incomplete. Thus it can mess up your syntax in cases where whitespace should be preserved as-is. It does preserve whitespace inside standard SQL string literals. But it can get confused by the non-standard PostgreSQL string literal syntax (which is the default setting in PostgreSQL 8 and below), the extended escape string syntax, quoted identifiers, and other similar constructs.
Of course, this caveat only applies to text written inside the SQL
quasiquoter; whitespace reduction is a compile-time computation and
thus will not touch the string parameter above, which is a run-time
value.
Also note that this will not work if the substring |] is contained
in the query.