Add update operation

src/sqlite3.erl

@@ -19,6 +19,7 @@
 -export([create_table/2, create_table/3]).
 -export([list_tables/0, list_tables/1, table_info/1, table_info/2]).
 -export([write/2, write/3]).
+-export([update/4, update/5]).
 -export([read/2, read/3]).
 -export([delete/2, delete/3]).
 -export([drop_table/1, drop_table/2]).
@@ -240,6 +241,36 @@ write(Tbl, Data) ->
 write(Db, Tbl, Data) ->
     gen_server:call(Db, {write, Tbl, Data}).
 
+%%--------------------------------------------------------------------
+%% @spec update (Tbl::atom (), Key::atom (), Value, Data) -> Result
+%%        Value = any ()
+%%        Data = [{Column::atom (), Value::string () | integer () | float ()}]
+%%        Result = {ok, ID} | Unknown
+%%        Unknown = term ()
+%% @doc
+%%    Updates rows into Tbl table such that the Value matches the 
+%%    value in Key with Data. Returns ID of the first updated 
+%%    record.
+%% @end
+%%--------------------------------------------------------------------
+update (Tbl, Key, Value, Data) ->
+  ?MODULE:update (?MODULE, Tbl, Key, Value, Data).
+
+%%--------------------------------------------------------------------
+%% @spec update (Db::atom (), Tbl::atom (), Key::atom (), Value, Data) -> Result
+%%        Value = any ()
+%%        Data = [{Column::atom (), Value::string () | integer () | float ()}]
+%%        Result = {ok, ID} | Unknown
+%%        Unknown = term ()
+%% @doc
+%%    Updates rows into Tbl table in Db dbase such that the Value 
+%%    matches the value in Key with Data. Returns ID of the first 
+%%    updated record.
+%% @end
+%%--------------------------------------------------------------------
+update (Db, Tbl, Key, Value, Data) ->
+  gen_server:call (Db, {update, Tbl, Key, Value, Data}).
+
 %%--------------------------------------------------------------------
 %% @spec read(Tbl::atom(), Key) -> [term()]
 %%         Key = {ColName::atom(), ColValue::term()}
@@ -397,6 +428,9 @@ handle_call({create_table, Tbl, Options}, _From, #state{port = Port} = State) ->
     Cmd = {sql_exec, SQL},
     Reply = exec(Port, Cmd),
     {reply, Reply, State};
+handle_call ({update, Tbl, Key, Value, Data}, _From, #state{port = Port} = State)->
+    Reply = exec (Port, {sql_exec, sqlite3_lib:update_sql (Tbl, Key, Value, Data)}),
+    {reply, Reply, State};
 handle_call({write, Tbl, Data}, _From, #state{port = Port} = State) ->
     % insert into t1 (data,num) values ('This is sample data',3);
     Reply = exec(Port, {sql_exec, sqlite3_lib:write_sql(Tbl, Data)}),

src/sqlite3_lib.erl

@@ -12,6 +12,7 @@
 -export([col_type/1]).
 -export([write_value_sql/1, write_col_sql/1]).
 -export([create_table_sql/2, write_sql/2, read_sql/3, delete_sql/3, drop_table/1]). 
+-export ([update_sql/4, update_set_sql/1, replace/1]).
 
 %%====================================================================
 %% API
@@ -19,6 +20,7 @@
 %%--------------------------------------------------------------------
 %% @spec col_type(Type :: term()) -> term()
 %% @doc Maps sqlite3 column type.
+%% @end
 %%--------------------------------------------------------------------
 -spec(col_type/1::(atom() | string()) -> atom() | string()).
 col_type(integer) ->
@@ -59,6 +61,7 @@ write_value_sql(Values) ->
 %%--------------------------------------------------------------------
 %% @spec write_col_sql([atom()]) -> string()
 %% @doc Creates the column/data stmt for SQL.
+%% @end
 %%--------------------------------------------------------------------
 -spec(write_col_sql/1::([atom()]) -> string()).
 write_col_sql(Cols) ->
@@ -67,12 +70,58 @@ write_col_sql(Cols) ->
 			end, Cols),
     string:join(StrCols, ",").
 
+%%--------------------------------------------------------------------
+%% @spec replace (String) -> string ()
+%%        String = string ()
+%% @doc Returns copy of String for which \" replaced with '
+%% @end
+%%--------------------------------------------------------------------
+-spec (replace/1::(string ()) -> string ()).
+replace ([34 | T]) ->
+  replace (T, ["'"]);
+replace ([H | T]) ->
+  replace (T, [binary_to_list (<<H>>)]).
+replace ([], L) ->
+  lists:flatten (lists:reverse (L));
+replace ([34 | T], L) ->
+  replace (T, ["'" | L]);
+replace ([H | T], L) ->
+  replace (T, [binary_to_list (<<H>>) | L]).
+
+%%--------------------------------------------------------------------
+%% @spec update_set_sql ([{Col, Value}]) -> string ()
+%%       Col = atom ()
+%%       Value = integer () | float () | string ()
+%% @doc 
+%%    Creates update set stmt.
+%%    Currently only supports integer, double/float and strings.
+%%    For strings \" replaced with '.
+%% @end
+%%--------------------------------------------------------------------
+-spec (update_set_sql/1::(any ()) -> string ()).
+update_set_sql (Data) ->
+  Set = lists:map (fun 
+      ({Col, Value}) when is_integer (Value) -> 
+        string:join (
+          [atom_to_list (Col), integer_to_list (Value)], " = ");
+      ({Col, Value}) when is_float (Value) -> 
+        string:join (
+          [atom_to_list (Col), integer_to_list (Value)], " = ");
+      ({Col, Value}) -> 
+        string:join (
+          [atom_to_list (Col), 
+            io_lib:format ("\"~s\"", [replace (Value)])], " = ") 
+    end,
+    Data),
+  string:join (Set, ", ").
+
 %%--------------------------------------------------------------------
 %% @spec create_table_sql(Tbl, [{ColName, Type}]) -> string()
 %%       Tbl = atom()
 %%       ColName = atom()
 %%       Type = string()
 %% @doc Generates a table create stmt in SQL.
+%% @end
 %%--------------------------------------------------------------------
 -spec(create_table_sql/2::(atom(), [{atom(), string()}]) -> string()).
 create_table_sql(Tbl, [{ColName, Type} | Tl]) ->
@@ -84,6 +133,29 @@ create_table_sql(Tbl, [{ColName, Type} | Tl]) ->
 		      end, Tl), ", ") ++ ");",
     lists:flatten(CT ++ Start ++ End).
 
+%%--------------------------------------------------------------------
+%% @spec update_sql (Tbl, Key, Value, Data) -> string ()
+%%        Tbl = atom ()
+%%        Key = atom ()
+%%        Value = atom ()
+%%        Data = [{ColName :: atom (), Value :: string () | integer () | float ()}]
+%% @doc 
+%%    Using Key as the column name and Data as list of column names 
+%%    and values pairs it creates the proper update SQL stmt for the 
+%%    record with matching Value.
+%% @end
+%%--------------------------------------------------------------------
+-type(sql_value() :: string() | integer() | float()).
+-spec (update_sql/4::(atom (), atom (), atom (), [{atom (), sql_value ()}]) -> string ()).
+update_sql (Tbl, Key, Value, Data) ->
+    lists:flatten (
+      io_lib:format ("UPDATE ~p SET ~s WHERE ~p = ~p;", 
+        [Tbl,
+         sqlite3_lib:update_set_sql (Data),
+         Key,
+         Value
+       ])).
+
 %%--------------------------------------------------------------------
 %% @spec write_sql(Tbl, Data) -> string()
 %%       Tbl = atom()
@@ -92,7 +164,6 @@ create_table_sql(Tbl, [{ColName, Type} | Tl]) ->
 %%      proper insertion SQL stmt.
 %% @end
 %%--------------------------------------------------------------------
--type(sql_value() :: string() | integer() | float()).
 -spec(write_sql/2::(atom(), [{atom(), sql_value()}]) -> string()).
 write_sql(Tbl, Data) ->
     {Cols, Values} = lists:unzip(Data),