library(mysql)

Predicates

sql_commit

Commit transaction (not implemented)

sql_delete(+Table, +Where, ++Attributelist, ++Valuelist, -RowsDeleted)

Delete tuple(s) from database

sql_desc(++Table)

Display the schema of the given relation

sql_exec(+Statement, -ReturnCode, -ReturnString, -RowsProcessed)

Execute an SQL statement

sql_external(++Table, ++CacheMode)

Make a database relation available as a predicate

sql_insert(+Table, ++Attributelist, ++Valuelist)

Insert tuple into database

sql_lastmsg(?ReturnCode, ?ReturnString, ?RowsProcessed)

Get the status of the last MySQL operation

sql_login(+Database, +Username, +Password)

Connect to a database

sql_login(+Database, +Username, +Password, +Serverhost)

Connect to a database

sql_logout

Disconnect from the database

sql_query(++Attributelist, ++Tables, +Where, +MoreOptions, ?Valuelist)

Query the database

sql_querydistinct(++Attributelist, ++Tables, +Where, +MoreOptions, ?Valuelist)

Query the database without duplicates

sql_rollback

Roll back a transaction (not implemented)

sql_select(++StatementList, +Valuelist)

Query the database using SQL SELECT statement

sql_showdb

Display all relations defined by the currently logged in user

Description

History

	Thomas H. Kolbe, Universitaet Bonn 
    

	Horst Samulowitz, Aachen 
    

	Joachim Schimpf, Imperial College London
    

Licence

This code may be freely copied and used. It may be used in commercial applications, but cannot be sold for a profit. If used within a commercial application, this code must be distributed for free along with the application. The same applies for any work derived by modifying this code.

General Hints

• Like in ECLiPSe, names (e.g. relation names) in MySQL are case sensitive.
• For all selection predicates, values of SQL type Char are returned as ECLiPSe atoms. If necessary, atom_string/2 can be used to convert them into ECLiPSe strings.
• For all selection predicates, null values of attributes are returned as the empty atom ''.
• External fact sets created via sql_external/2 do not honour schema modifications that are done while the database is connected. In particular, this can cause problems when attributes of the underlying relation are removed or renamed, or when the whole relation is removed or renamed. Since these actions can be performed from outside ECLiPSe, and since there is no notification mechanism, no automatic update is possible.
• In addition, cached relations exhibit a version problem, since the cached facts are no longer up to date after database manipulations. In this case, the cached relation must either be recomputed by invoking sql_external(Name, cache) again, or the relation should be left uncached, using sql_external(Name, nocache).

Error Messages

type error in ...

This is an Eclipse error message indicating a type conflict. It can have several causes. Usually, some argument of an interface predicate has the wrong type.

instantiation fault in ...

This is an Eclipse error message indicating a missing instantiation. It can have several causes. Usually, some argument of an interface predicate is uninstantiated, or not sufficiently instantiated. E.g. sql_select/2 requires a list skeleton of fixed length.

Error: varlist too short!

The variable list and the attribute list in sql_query/5 or sql_querydistinct/5 have different lengths.

Error: attributelist too short!

The variable list and the attribute list in sql_query/5 or sql_querydistinct/5 have different lengths.

Error: attributelist must not be empty!

An empty attribute list was supplied, at least one is required.

Error: varlist must not be empty!

An empty variable list was supplied, at least one element is required.

Error: Cursor limit exhausted (max. no. is XX)!

The maximum number XX of open concurrently open cursors was exceeded. The first possibility to get around this problem is to rearrange the queries such that fewer open cursors are required, and make sure that resatisfiable selection predicates are cut or failed over. Another possible solution is to a priori retrieve all tuples into a list (using findall/3), and then process the list using member/2. After findall/3, the cursor is closed and can be reused. The maimum number of cursors can be increased by modifying the interface source (mysql.c) and recompile.

Error: too many columns selected!

The maximum number of columns in a projection was exceeded in sql_query/5, sql_querydistinct/5 or sql_select/2.

Error: select statement must not be empty!

An empty list was given to sql_select/2.

Error: attributelist and variablelist must have the same length!

In sql_select/2, the number of projected attributes in the selection command must correspond to the length of the result variable list.

Error: cursor# too big (range is 0-XX)!

This error should never occur and would indicate an internal problem in the interface code.

MySQL-Fehler: ...

This is an error message from MySQL. Refer to the MySQL documentation.

About

• Author: Thomas H Kolbe, Universitaet Bonn
• Date: $Date$