Module Database.CDBI.Connection

fromSQLResult :: Either DBError a -> a   

Gets the value of an SQLResult. If there is no result value but a database error, the error is raised.

printSQLResults :: Show a => Either DBError [a] -> IO ()   

Print an SQLResult list, i.e., print either the DBError or the list of result elements.

runDBAction :: DBAction a -> Connection -> IO (Either DBError a)   

Runs a DBAction on a connection.

runInTransaction :: DBAction a -> DBAction a   

Run a DBAction as a transaction. In case of an error, it will rollback all changes, otherwise, the changes are committed. The transaction is also checked whether foreign key errors have been introduced so that a transaction which introduces foreign key errors will never be committed.

Example call:

(runInTransaction act conn)

Parameters:

• act : The DBAction
• conn : The Connection to the database on which the transaction shall be executed.

(>+=) :: DBAction a -> (a -> DBAction b) -> DBAction b   

Connects two DBActions. When executed this function will execute the first DBAction and then execute the second applied to the result of the first action. A database error will stop either action.

Example call:

(x >+= y)

Parameters:

• x : The DBAction that will be executed first
• y : The DBAction hat will be executed afterwards

Returns:

A DBAction that wille execute both DBActions. The result is the result of the second DBAction.

Further infos:

• defined as left-associative infix operator with precedence 1

(>+) :: DBAction a -> DBAction b -> DBAction b   

Connects two DBActions but ignore the result of the first.

Further infos:

• defined as left-associative infix operator with precedence 1

returnDB :: Either DBError a -> DBAction a   

Returns an SQLResult.

failDB :: DBError -> DBAction a   

A failed DBAction with a specific error.

select :: String -> [SQLValue] -> [SQLType] -> DBAction [[SQLValue]]   

Execute a query where the result of the execution is returned.

Example call:

(select query values types conn)

Parameters:

• query : The SQL Query as a String, might have ? as placeholder
• values : A list of SQLValues that replace the ? placeholder
• types : A list of SQLTypes that describe the types of the result-tables (e.g. "select * from exampletable" and [SQLTypeInt, SQLTypeFloat, SQLTypeString] when the table exampletable has three columns of type Int, Float and String.) The order of the list has to be the same as the order of the columns in the table
• conn : A Connection to a database where the query will be executed

Returns:

A Result with a list of SQLValues which types correspond to the SQLType-List that was given as a parameter if the execution was successful, otherwise an Error

execute :: String -> [SQLValue] -> DBAction ()   

execute a query without a result

Example call:

(execute query values conn)

Parameters:

• query : The SQL Query as a String, might have ? as placeholder
• values : A list of SQLValues that replace the ? placeholder
• conn : A Connection to a database where the query will be executed

Returns:

An empty if the execution was successful, otherwise an error

executeMultipleTimes :: String -> [[SQLValue]] -> DBAction ()   

Executes a query multiple times with different SQLValues without a result

Example call:

(executeMultipleTimes query values)

Parameters:

• query : The SQL Query as a String, might have ? as placeholder
• values : A list of lists of SQLValues that replace the ? placeholder (one list for every execution)

Returns:

A void result if every execution was successful, otherwise an Error (meaning at least one execution failed). As soon as one execution fails, the rest wont be executed.

connectSQLite :: String -> IO Connection   

Connect to a SQLite Database

Example call:

(connectSQLite str)

Parameters:

• str : name of the database (e.g. "database.db")

Returns:

A connection to a SQLite Database

disconnect :: Connection -> IO ()   

Disconnect from a database.

writeConnection :: String -> Connection -> IO ()   

Write a String to a Connection.

begin :: DBAction ()   

Begin a transaction. Inside a transaction, foreign key constraints are checked.

commit :: DBAction ()   

Commit a transaction.

rollback :: DBAction ()   

Rollback a transaction.

setForeignKeyCheck :: Bool -> DBAction ()   

Turn on/off checking of foreign key constraints (SQLite3).

runWithDB :: String -> DBAction a -> IO (Either DBError a)   

Executes an action dependent on a connection on a database by connecting to the datebase. The connection will be kept open and re-used for the next action to this database.

Example call:

(runWithDB str action)

Parameters:

• str : name of the database (e.g. "database.db")
• action : an action parameterized over a database connection

Returns:

the result of the action

executeRaw :: String -> [String] -> DBAction [[String]]   

Executes an SQL statement. The statement may contain ? placeholders and a list of parameters which should be inserted at the respective positions. The result is a list of list of strings where every single list represents a row of the result.

getColumnNames :: String -> DBAction [String]   

Returns a list with the names of every column in a table The parameter is the name of the table.

valueToString :: SQLValue -> String