- Documentation
- Reference manual
- Packages
- Constraint Query Language A high level interface to SQL databases
- library(cql/cql): CQL - Constraint Query Language
- Examples
- Simple INSERT
- Simple INSERT with retrieval of identity of the inserted
- Simple DELETE
- Simple SELECT
- Simple UPDATE
- WHERE with arithmetic comparison
- Simple INNER JOIN
- Arithmetic UPDATE with an INNER JOIN and a WHERE restriction
- Confirm row does not exist
- Aggregation - Count
- Aggregation - Sum
- Aggregation - Average
- Maximum Value
- Minimum Value
- Aggregation requiring GROUP BY
- INNER JOIN with an aggregation sub-query where the sub-query is constrained by a shared variable from the main query
- INNER JOIN in an aggregation sub-query
- Negation
- EXISTS
- Left Outer Join
- List-based Restrictions
- Compile time in-list constraint
- Disjunction resulting in OR in WHERE clause
- Disjunction resulting in different joins (implemented as a SQL UNION)
- Disjunction resulting in different SELECT attributes (implemented as separate ODBC queries)
- ORDER BY
- DISTINCT
- SELECT with NOT NULL restriction
- First N
- Self JOIN
- Removing null comparisions
- Three table JOIN
- Three table JOIN with NOLOCK locking hint
- SELECT with LIKE
- Writing exceptions directly to the database
- TOP N is Parametric
- Using compile_time_goal/1
- ON
- Expressions In Where Restrictions
- Explicitly avoid the "No WHERE restriction" message
- HAVING
- INSERT and UPDATE value in-line formatting
- Negations in WHERE Clauses
- Predicate-generated Attribute Values
- INSERT from SELECT
- Examples
- library(cql/cql): CQL - Constraint Query Language
- Constraint Query Language A high level interface to SQL databases
1.7.38 ON
CQL supports both constant and shared variable join specifications. This is particularly useful when specifying outer joins.
Example
{[],
se_lt_x :: [a-UserNameA,
b-RealName,
d-FavouriteColour]
*==
se_lt_x :: [a-UserNameB,
e-FavouriteFood] on( UserNameA == UserNameB,
FavouriteColour == FavouriteFood,
FavouriteFood == 'ORANGE')}
All the CQL comparison operators, <, =<, ==, =~, \=~, \==, >=, >
can be used in ON specifications.
For example:
{[],
se_lt_z :: [i-J1, k-K]
*==
se_lt_x :: [c-J1, a-A, b-B] on A \== 'A1'},