## GdaDataModelQuery

GdaDataModelQuery — An implementation of GdaDataModel based on a SELECT query

## Synopsis

                        GdaDataModelQuery;
                        GdaDataModelQueryClass;
                        GdaDataModelQueryPrivate;
    GdaDataModel*       gda_data_model_query_new            (GdaQuery *query);
    GdaParameterList*   gda_data_model_query_get_parameter_list
                                                            (GdaDataModelQuery *model);
    gboolean            gda_data_model_query_refresh        (GdaDataModelQuery *model,
                                                             GError **error);
    gboolean            gda_data_model_query_set_modification_query
                                                            (GdaDataModelQuery *model,
                                                             const gchar *query,
                                                             GError **error);
    gboolean            gda_data_model_query_compute_modification_queries
                                                            (GdaDataModelQuery *model,
                                                             const gchar *target,
                                                             GdaDataModelQueryOptions options,
                                                             GError **error);

## Object Hierarchy

      GObject
       +----GdaObject
             +----GdaDataModelQuery

## Implemented Interfaces

GdaDataModelQuery implements GdaDataModel.

## Properties

      "delete-query"             GdaQuery*             : Read / Write
      "insert-query"             GdaQuery*             : Read / Write
      "query"                    GdaQuery*             : Read / Write / Construct Only
      "update-query"             GdaQuery*             : Read / Write
      "use-transaction"          gboolean              : Read / Write / Construct

## Description

The GdaDataModelQuery data model simply stores the values returned by a SELECT query. The connection used to execute the SELECT query (given when the object is constructed) is the same as the one provided th the GdaDict object to which the query relates.

## Details

### GdaDataModelQuery

    typedef struct _GdaDataModelQuery GdaDataModelQuery;

### GdaDataModelQueryClass

    typedef struct {
    	GdaObjectClass             parent_class;
    } GdaDataModelQueryClass;

### GdaDataModelQueryPrivate

    typedef struct _GdaDataModelQueryPrivate GdaDataModelQueryPrivate;

### gda_data_model_query_new ()

    GdaDataModel*       gda_data_model_query_new            (GdaQuery *query);

Creates a new GdaDataModel object using the data returned by the execution of the `query` SELECT query.

`query` : | a SELECT query
Returns : | a pointer to the newly created GdaDataModel.

### gda_data_model_query_get_parameter_list ()

    GdaParameterList*   gda_data_model_query_get_parameter_list
                                                            (GdaDataModelQuery *model);

If some parameters are required to execute the SELECT query used in the `model` data model, then returns the GdaParameterList used; otherwise does nothing and returns `NULL`.

`model` : | a GdaDataModelQuery data model
Returns : | a GdaParameterList object, or `NULL`

### gda_data_model_query_refresh ()

    gboolean            gda_data_model_query_refresh        (GdaDataModelQuery *model,
                                                             GError **error);

(Re)-runs the SELECT query to update the contents of `model`

`model` : | a GdaDataModelQuery data model
`error` : | a place to store errors, or `NULL`
Returns : | TRUE if no error occurred

### gda_data_model_query_set_modification_query ()

    gboolean            gda_data_model_query_set_modification_query
                                                            (GdaDataModelQuery *model,
                                                             const gchar *query,
                                                             GError **error);

Sets the modification query to be used by `model` to actually perform any change to the dataset in the database.

The provided query (the `query` SQL) must be either a INSERT, UPDATE or DELETE query. It can contain parameters, and the parameters named '[+-]<num>' will be replaced when the query is run:

- a parameter named +<num> will take the new value set at the <num>th column in `model`

- a parameter named -<num> will take the old value set at the <num>th column in `model`

Please note that the "+0" and "-0" parameters names are valid and will respectively take the new and old values of the first column of `model`.

Examples of queries are: "INSERT INTO orders (customer, creation_date, delivery_before, delivery_date) VALUES (## / *name:'Customer' type:integer* /, date('now'), ## / *name:"+2" type:date nullok:TRUE * /, NULL)", "DELETE FROM orders WHERE id = ## / *name:"-0" type:integer* /" and "UPDATE orders set id=## / *name:"+0" type:integer* /, delivery_before=## / *name:"+2" type:date nullok:TRUE* /, delivery_date=## / *name:"+3" type:date nullok:TRUE* / WHERE id=## / *name:"-0" type:integer* /"

`model` : | a GdaDataModelQuery data model
`query` : | the SQL code for a query
`error` : | a place to store errors, or `NULL`
Returns : | TRUE if no error occurred.

### gda_data_model_query_compute_modification_queries ()

    gboolean            gda_data_model_query_compute_modification_queries
                                                            (GdaDataModelQuery *model,
                                                             const gchar *target,
                                                             GdaDataModelQueryOptions options,
                                                             GError **error);

Try to compute the INSERT, DELETE and UPDATE queries; any previous modification query will be discarded.

If specified, the table which will be updated is the one represented by the `target`.

If `target` is `NULL`, then an error will be returned if `model`'s SELECT query has more than one target.

`model` : | a GdaDataModelQuery object
`target` : | the target table to modify, or `NULL`
`options` : | options to specify how the queries must be built in some special cases
`error` : | a place to store errors or `NULL`
Returns : | TRUE if the INSERT, DELETE and UPDATE queries have been computed.

## Property Details

### The `"delete-query"` property

      "delete-query"             GdaQuery*             : Read / Write

DELETE Query to be executed to remove data.

### The `"insert-query"` property

      "insert-query"             GdaQuery*             : Read / Write

INSERT Query to be executed to add data.

### The `"query"` property

      "query"                    GdaQuery*             : Read / Write / Construct Only

SELECT Query to be executed to populate the model with data.

### The `"update-query"` property

      "update-query"             GdaQuery*             : Read / Write

UPDATE Query to be executed to update data.

### The `"use-transaction"` property

      "use-transaction"          gboolean              : Read / Write / Construct

Run modification queries within a transaction.

Default value: FALSE