fix: prevent SQL error "Property 'MS_Description' already exists"

Fire either sp_addextendedproperty or sp_updateextendedproperty for setting a MS SQL column comment

Refs #2552

Author: ansgarbecker

source/dbstructures.mssql.pas

@@ -455,6 +455,31 @@ function TMsSqlProvider.GetSql(AId: TQueryId): string;
     qLikeCompare: Result := '%s LIKE %s';
     qAddColumn: Result := 'ADD %s';
     qChangeColumn: Result := 'ALTER COLUMN %s %s';
+    qSetColumnComment: Result := 'IF NOT EXISTS (' + sLineBreak +
+      '    SELECT 1' + sLineBreak +
+      '    FROM fn_listextendedproperty (' + sLineBreak +
+      '        N''MS_Description'',' + sLineBreak +
+      '        N''SCHEMA'', :EscapedSchema,' + sLineBreak +
+      '        N''TABLE'',  :EscapedName,' + sLineBreak +
+      '        N''COLUMN'', :TargetColumn' + sLineBreak +
+      '    )' + sLineBreak +
+      ')' + sLineBreak +
+      'BEGIN' + sLineBreak +
+      '    EXEC sys.sp_addextendedproperty' + sLineBreak +
+      '        @name        = N''MS_Description'',' + sLineBreak +
+      '        @value       = :NewComment,' + sLineBreak +
+      '        @level0type  = N''SCHEMA'', @level0name = :EscapedSchema,' + sLineBreak +
+      '        @level1type  = N''TABLE'',  @level1name = :EscapedName,' + sLineBreak +
+      '        @level2type  = N''COLUMN'', @level2name = :TargetColumn' + sLineBreak +
+      'END' + sLineBreak +
+      'ELSE BEGIN' + sLineBreak +
+      '    EXEC sys.sp_updateextendedproperty' + sLineBreak +
+      '        @name        = N''MS_Description'',' + sLineBreak +
+      '        @value       = :NewComment,' + sLineBreak +
+      '        @level0type  = N''SCHEMA'', @level0name = :EscapedSchema,' + sLineBreak +
+      '        @level1type  = N''TABLE'',  @level1name = :EscapedName,' + sLineBreak +
+      '        @level2type  = N''COLUMN'', @level2name = :TargetColumn' + sLineBreak +
+      'END';
     qSessionVariables: Result := 'SELECT comment, value FROM master.dbo.syscurconfigs ORDER BY comment';
     qGlobalVariables: Result := 'SELECT comment, value FROM master.dbo.syscurconfigs ORDER BY comment';
     qISSchemaCol: Result := '%s_CATALOG';

source/dbstructures.pas

@@ -40,7 +40,7 @@ interface
   TQueryId = (qDatabaseTable, qDatabaseTableId, qDatabaseDrop,
     qDbObjectsTable, qDbObjectsCreateCol, qDbObjectsUpdateCol, qDbObjectsTypeCol,
     qEmptyTable, qRenameTable, qRenameView, qCurrentUserHost, qLikeCompare,
-    qAddColumn, qChangeColumn, qRenameColumn, qForeignKeyEventAction,
+    qAddColumn, qChangeColumn, qRenameColumn, qSetColumnComment, qForeignKeyEventAction,
     qGlobalStatus, qCommandsCounters, qSessionVariables, qGlobalVariables,
     qISSchemaCol,
     qUSEQuery, qKillQuery, qKillProcess,

source/table_editor.pas

@@ -647,6 +647,7 @@ function TfrmTableEditor.ComposeAlterStatement: TSQLBatch;
   Constraint: TCheckConstraint;
   Node: PVirtualNode;
   Conn: TDBConnection;
+  Params: TStringMap;
 
   procedure FinishSpecs;
   begin
@@ -660,7 +661,7 @@ function TfrmTableEditor.ComposeAlterStatement: TSQLBatch;
   procedure AddQuery(Query: String);
   begin
     FinishSpecs;
-    SQL := SQL + Format(Query, [DBObject.QuotedName]) + ';' + CRLF;
+    SQL := SQL + Format(Query, [DBObject.QuotedName]) + ';' + sLineBreak;
   end;
 begin
   // Compose ALTER query, called by buttons and for SQL code tab
@@ -778,12 +779,10 @@ function TfrmTableEditor.ComposeAlterStatement: TSQLBatch;
               Specs.Add(Format(AddColBase, [ColSpec]));
             end;
           end;
-          AddQuery('EXECUTE sp_addextendedproperty '+Conn.EscapeString('MS_Description')+', '+
-            Conn.EscapeString(Col.Comment)+', '+
-            Conn.EscapeString('Schema')+', '+Conn.EscapeString(DBObject.Schema)+', '+
-            Conn.EscapeString('table')+', '+Conn.EscapeString(DBObject.Name)+', '+
-            Conn.EscapeString('column')+', '+Conn.EscapeString(Col.Name)
-            );
+          Params := DBObject.AsStringMap;
+          Params.Add('NewComment', Conn.EscapeString(Col.Comment));
+          Params.Add('TargetColumn', Conn.EscapeString(Col.Name));
+          AddQuery(Conn.SqlProvider.GetSql(qSetColumnComment, Params));
         end;
 
         ngPgSQL: begin