Oracleデータベースは、データが完全な場合にフィールドの精度を変更することを保証します.

orderテーブルのtotalフィールドの精度を変更するとします。

alter table order modify (total NUMBER(24,4) NOT NULL);

declare
  size Int;
Begin
  size := 0;
  Select Count(1) Into size From SqlUpgradeLog Where ID = '  id';
  If size = 0 Then
  	--total   tmp_total
	execute immediate 'alter table order rename column total to tmp_total';
	
	--  total  ，           
	execute immediate 'alter table order add total NUMBER(24,4) default 0 NOT NULL';
	
	--       total
	execute immediate 'update order set total = tmp_total';
	
	--  tmp_total
	execute immediate 'alter table order drop column tmp_total';
	
    Insert Into SqlUpgradeLog(id,time,desc) values('  id',sysdate,'  ');
	commit;
  End If;
End;

declare
  size Int;
Begin
  size := 0;
  Select Count(1) Into size From SqlUpgradeLog Where ID = '  id';
  If size = 0 Then
 	--total   tmp_total
	execute immediate 'alter table order rename column total to tmp_total';
	
	--  total  ，           
	execute immediate 'alter table order add total NUMBER(24,4) NULL';
	
	--       total
	execute immediate 'update order set total = tmp_total';
	
	-- total  not null
	execute immediate 'alter table order modify (total NUMBER(24,4) NOT NULL)';
	
	--  tmp_total
	execute immediate 'alter table order drop column tmp_total';
	
    Insert Into SqlUpgradeLog(id,time,desc) values('  id',sysdate,'  ');
	commit;
  End If;
End;