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MySQL 4.0.1 and above allow moving a columns position within an ALTER TABLE statement. Use that to overcome various risks of the manual mechanism for older servers.

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This commit is contained in:
Ansgar Becker
2007-09-03 09:38:20 +00:00
parent 21a7d22af9
commit 16c0ac36b3
1 changed files with 39 additions and 27 deletions
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66
source/fieldeditor.pas
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@ -350,13 +350,16 @@ var
strLengthSet,
strDefault,
strPosition,
fielddef : String;
fielddef,
sql_alterfield : String;
cwin : TMDIChild;
begin
// Apply Changes to field-definition
cwin := Mainform.ChildWin;
// move field if position changed
if (ComboBoxPosition.ItemIndex > -1) and (FMode in [femFieldUpdate]) then
if (ComboBoxPosition.ItemIndex > -1) and (FMode in [femFieldUpdate]) and (cwin.mysql_version < 40001) then
begin // Move field position
if MessageDLG('You are about to move a field''s position in the table-structure. While there is no handy one-query-method in MySQL to do that, this will be done in 4 steps:'+CRLF+
' 1. Adding a temporary field at the specified position'+CRLF+
@ -418,8 +421,6 @@ begin
strNotNull + // Not Null
strAutoIncrement; // Auto_increment
cwin := Mainform.ChildWin;
if (FMode = femFieldAdd) then begin
cwin.ExecUpdateQuery(
'ALTER TABLE ' + mainform.mask(cwin.ActualTable) + ' ' + // table
@ -428,31 +429,42 @@ begin
strPosition // Position
);
end else if (FMode = femFieldUpdate) then begin
cwin.ExecUpdateQuery(
'ALTER TABLE ' + mainform.mask(cwin.ActualTable) + ' ' + // table
'CHANGE ' + mainform.mask(FFieldName) + ' ' + // old name
mainform.mask(EditFieldName.Text) + ' ' + // new name
fielddef
);
//ShowMessageFmt ('ComboBox position: %d',[ComboBoxPosition.ItemIndex]);
if ComboBoxPosition.ItemIndex > -1 then begin
// Move field position
cwin.ExecUpdateQuery(
'ALTER TABLE ' + mainform.mask(cwin.ActualTable) + ' ' + // table
'ADD ' + mainform.mask(TEMPFIELDNAME) + ' ' + // new name
fielddef +
strPosition // Position
);
cwin.ExecUpdateQuery('UPDATE ' + mainform.mask(cwin.ActualTable) + ' SET '+mainform.mask(TEMPFIELDNAME)+'='+mainform.mask(EditFieldName.Text));
cwin.ExecUpdateQuery('ALTER TABLE ' + mainform.mask(cwin.ActualTable) + ' DROP '+mainform.mask(EditFieldName.Text));
cwin.ExecUpdateQuery(
'ALTER TABLE ' + mainform.mask(cwin.ActualTable) + ' ' +
'CHANGE ' + mainform.mask(TEMPFIELDNAME) + ' ' +
sql_alterfield := 'ALTER TABLE ' + mainform.mask(cwin.ActualTable) + ' ' +
'CHANGE ' + mainform.mask(FFieldName) + ' ' +
mainform.mask(EditFieldName.Text) + ' ' +
fielddef
);
fielddef;
if cwin.mysql_version >= 40001 then
begin
// MySQL 4.0.1+ allows column moving in a ALTER TABLE statement.
// @see http://dev.mysql.com/doc/refman/4.1/en/alter-table.html
cwin.ExecUpdateQuery( sql_alterfield + strPosition );
end
else begin
// Use manual mechanism on older servers
cwin.ExecUpdateQuery( sql_alterfield );
//ShowMessageFmt ('ComboBox position: %d',[ComboBoxPosition.ItemIndex]);
if ComboBoxPosition.ItemIndex > -1 then begin
// Move field position
cwin.ExecUpdateQuery(
'ALTER TABLE ' + mainform.mask(cwin.ActualTable) + ' ' + // table
'ADD ' + mainform.mask(TEMPFIELDNAME) + ' ' + // new name
fielddef +
strPosition // Position
);
cwin.ExecUpdateQuery('UPDATE ' + mainform.mask(cwin.ActualTable) + ' SET '+mainform.mask(TEMPFIELDNAME)+'='+mainform.mask(EditFieldName.Text));
cwin.ExecUpdateQuery('ALTER TABLE ' + mainform.mask(cwin.ActualTable) + ' DROP '+mainform.mask(EditFieldName.Text));
cwin.ExecUpdateQuery(
'ALTER TABLE ' + mainform.mask(cwin.ActualTable) + ' ' +
'CHANGE ' + mainform.mask(TEMPFIELDNAME) + ' ' +
mainform.mask(EditFieldName.Text) + ' ' +
fielddef
);
end;
end;
end;
cwin.ShowTableProperties(self);