Database.HSQL

A Connection type represents a connection to a database, through which you can operate on the it. In order to create the connection you need to use the connect function from the module for your prefered backend.

disconnect :: Connection -> IO ()

Closes the connection. Performing disconnect on a connection that has already been closed has no effect. All other operations on a closed connection will fail.

Command Execution Functions

Once a connection to a database has been successfully established, the functions described here are used to perform SQL queries and commands.

execute

:: Connection	the database connection
-> String	the text of SQL command
-> IO ()
Submits a command to the database.

data Statement

The Statement type represents a result from the execution of given SQL query.

query

:: Connection	the database connection
-> String	the text of SQL query
-> IO Statement	the associated statement. Must be closed with the `closeStatement` function
Executes a query and returns a result set

closeStatement :: Statement -> IO ()

closeStatement stops processing associated with a specific statement, closes any open cursors associated with the statement, discards pending results, and frees all resources associated with the statement. Performing closeStatement on a statement that has already been closed has no effect. All other operations on a closed statement will fail.

fetch :: Statement -> IO Bool

fetch fetches the next rowset of data from the result set. The values from columns can be retrieved with getFieldValue function.

Retrieving Statement values and types

type FieldDef = (String, SqlType, Bool)

data SqlType

Constructors

SqlChar Int
SqlVarChar Int
SqlLongVarChar Int
SqlText
SqlWChar Int
SqlWVarChar Int
SqlWLongVarChar Int
SqlDecimal Int Int
SqlNumeric Int Int
SqlSmallInt
SqlMedInt
SqlInteger
SqlReal
SqlFloat
SqlDouble
SqlBit
SqlTinyInt
SqlBigInt
SqlBinary Int
SqlVarBinary Int
SqlLongVarBinary Int
SqlDate
SqlTime
SqlTimeTZ
SqlAbsTime
SqlRelTime
SqlTimeInterval
SqlAbsTimeInterval
SqlTimeStamp
SqlDateTime
SqlDateTimeTZ
SqlYear
SqlSET
SqlENUM
SqlBLOB
SqlMoney
SqlINetAddr
SqlCIDRAddr
SqlMacAddr
SqlPoint
SqlLSeg
SqlPath
SqlBox
SqlPolygon
SqlLine
SqlCircle
SqlUnknown Int	HSQL returns `SqlUnknown tp` for all columns for which it cannot determine the right type. The `tp` here is the internal type code returned from the backend library

Instances

Eq SqlType

Show SqlType

class SqlBind a

getFieldValueMB

:: SqlBind a
=> Statement
-> String	Field name
-> IO (Maybe a)	Field value or Nothing
Retrieves the value of field with the specified name. The returned value is Nothing if the field value is `null`.

getFieldValue

:: SqlBind a
=> Statement
-> String	Field name
-> IO a	Field value
Retrieves the value of field with the specified name. If the field value is `null` then the function will throw `SqlFetchNull` exception.

getFieldValue'

:: SqlBind a
=> Statement
-> String	Field name
-> a	Default field value
-> IO a	Field value
Retrieves the value of field with the specified name. If the field value is `null` then the function will return the default value.

getFieldValueType :: Statement -> String -> (SqlType, Bool)

Returns the type and the nullable flag for field with specified name

getFieldsTypes :: Statement -> [(String, SqlType, Bool)]

Returns the list of fields with their types and nullable flags

Transactions

inTransaction

:: Connection
-> (Connection -> IO a)	an action
-> IO a	the returned value is the result returned from action
The `inTransaction` function executes the specified action in transaction mode. If the action completes successfully then the transaction will be commited. If the action completes with an exception then the transaction will be rolled back and the exception will be throw again.

SQL Exceptions handling

data SqlError

Constructors

SqlError

seState :: String
seNativeError :: Int
seErrorMsg :: String

SqlNoData

SqlInvalidHandle

SqlStillExecuting

SqlNeedData

SqlBadTypeCast

seFieldName :: String
seFieldType :: SqlType

SqlFetchNull

seFieldName :: String

SqlUnknownField

seFieldName :: String

SqlUnsupportedOperation

SqlClosedHandle

Instances

Typeable SqlError

Show SqlError

catchSql :: IO a -> (SqlError -> IO a) -> IO a

handleSql :: (SqlError -> IO a) -> IO a -> IO a

sqlExceptions :: Exception -> Maybe SqlError

Utilities

forEachRow

:: (Statement -> s -> IO s)	an action
-> Statement	the statement
-> s	initial state
-> IO s	final state
The `forEachRow` function iterates through the result set in `Statement` and executes the given action for each row in the set. The function closes the `Statement` after the last row processing or if the given action raises an exception.

forEachRow' :: (Statement -> IO ()) -> Statement -> IO ()

The forEachRow' function is analogous to forEachRow but doesn't provide state. The function closes the Statement after the last row processing or if the given action raises an exception.

collectRows :: (Statement -> IO a) -> Statement -> IO [a]

The collectRows function iterates through the result set in Statement and executes the given action for each row in the set. The values returned from action are collected and returned as list. The function closes the Statement after the last row processing or if the given action raises an exception.

Metadata

tables

:: Connection	Database connection
-> IO [String]	The names of all tables in the database.
List all tables in the database.

describe

:: Connection	Database connection
-> String	Name of a database table
-> IO [FieldDef]	The list of fields in the table
List all columns in a table along with their types and `nullable` flags