SQL 的一些基本操作

在一张表里取每种类型的记录N条的SQL语句。

SELECT * FROM tabelname AS a WHERE a.id in(select top N from tabelname where id=a.id order by id) ORDER BY [id];

插入一表中列到另一个表

-------------
insert into test(image)
SELECT biglb.bigimages
FROM biglb

复制一表中列到另一个表（两个表中记录数、类型一样）
---------------*********************-----------------

在sql中，如果想将表t1字段d1的值全部复制到表t2字段d2下
(d1和d2的记录数、类型一样）

update t2 set a.d2=b.d1 from t2 as a,t1 as b

--------------------------------------------------------------------------

int iResult;
          iResult = ds.E...("select top 30 * from table1 where weizhi> 0")
          if(iResult<30)
          {
                ds.E....("select * from table1 where ... union select top (30 - iResult) * from table2 where...");
          }

        SqlConnection sql = new
        SqlDataAdapter objAdapter = new SqlDataAdapter();
        objAdapter.TableMappings.Add("Table", CustomerData.ACCEPTER_TABLE);
        SqlCommand objCommand = new SqlCommand("select * from t1 where weizhi > 0 ", Pro_GetSqlConnect);
        DataSet ds = new DataSet();
        objAdapter.SelectCommand = objCommand;
        objAdapter.Fill(ds);
        return ds;

        DataRowCollection rows = ds.Tables["t1"].Rows;

         insert into x3(xid, name, gdate,weizhi)
select a.id , a.name, a.gdate , a.weizhi from x1 as a where a.weizhi > 0 union select top 27 a.id,a.name,a.gdate,a.weizhi from x2 as a order by a.gdate desc