Question

I am doing some changes on my table and I couldn't figure out the problem. This is my SQL script;

ALTER TABLE X ALTER COLUMN X_ID RESTART WITH (SELECT MAX(X_ID) FROM X);

Altough I used AS instead of WITH and tried other combinations, I couldn't find the exact syntax. (By the way, I cannot set this property in the initialization, I got to do it after creation of the table )

Answer 1

查看ALTER TABLE的语法时，您会发现只能使用常量，例如＆＃34; RESTART WITH 12345＆＃34;。查询本身是不可能的。对于自动化，您需要将其分解，使用变量，生成ALTER语句并执行它。

Answer 2

假设这是针对DB2 for LUW，您可以使用一些动态SQL自动执行重置身份值的过程：

begin
 declare curmax bigint;
 for r as select tabschema, tabname, colname, nextcachefirstvalue, seqid 
          from syscat.colidentattributes where tabschema = current_schema
  do
   prepare s from 
    'select max(' || r.colname || ') from ' || 
     rtrim(r.tabschema) || '.' || r.tabname;
   begin
    declare c cursor for s;
    open c;
    fetch c into curmax;
    close c;
   end;
   if curmax >= r.nextcachefirstvalue
   then
    execute immediate 
     'alter table ' || rtrim(r.tabschema) || '.' || r.tabname ||
     ' alter column ' || r.colname || ' restart with ' || varchar(curmax+1);
   end if;
  end for;
end

如果您的身份不是整数，则可能需要更改curmax的数据类型，并针对syscat.colidentattributes调整查询以使用相应的模式名称。

Restart initial id of table with using MAX() method

2 个答案: