请教，这段SQL语句应该怎么写？

Question

private void Search()
        {
            string ssql = "select distinct a.STAFF_ID,a.CNNAME,a.DEPT,a.TECHPOS,a.EDULEVEL,a.ATTACH_DATE,b.M_SKILL,b.M_TYPE,c.LANGUAGE";
            ssql += " from D_STAFF_BASE a,D_SKILL_VIEW b,D_STAFF_LANG_ABILITY c";
            
            //根据姓名查询
            if (this.TextBox1.Text.Trim() != "")
            {
               
                ssql += " where a.CNNAME='"+this.TextBox1.Text.Trim()+"'";
            }            //根据技能查询
            if (this.TextBox3.Text.Trim() != "")
            {
                
                ssql += " where b.M_SKILL='"+this.TextBox3.Text.Trim()+"'or b.M_TYPE='"+this.TextBox3.Text.Trim()+"'";
            }            //根据语言查询
            if (this.Languageddl.SelectedValue!="")
            {
                ssql += " where c.LANGUAGE='"+this.Languageddl.DataValueField+"'";
            }
            
            //根据职称查询
            if (this.Techposddl.SelectedValue != "")
            {
                ssql += " where a.TECHPOS='"+this.Techposddl.DataValueField+"'";
            }
            if (this.Deptddl.SelectedValue != "")
            {
                ssql += " where a.DEPT='"+this.Deptddl.DataValueField+"'";
            }  
            //GridView1.DataSourceID = "SqlDataSource1";
            this.SqlDataSource1.SelectCommand = ssql;
            this.DataBind();
 
        }
根据不同的情况查询，我的这个SQL语句老是写不对，应该怎么写啊？

Answer 1

private void Search()
        {
            string ssql = "select distinct a.STAFF_ID,a.CNNAME,a.DEPT,a.TECHPOS,a.EDULEVEL,a.ATTACH_DATE,b.M_SKILL,b.M_TYPE,c.LANGUAGE";
            ssql += " from D_STAFF_BASE a,D_SKILL_VIEW b,D_STAFF_LANG_ABILITY c where 1=1 ";
            
            //根据姓名查询
            if (this.TextBox1.Text.Trim() != "")
            {
               
                ssql += " and a.CNNAME='"+this.TextBox1.Text.Trim()+"'";
            }            //根据技能查询
            if (this.TextBox3.Text.Trim() != "")
            {
                
                ssql += " and b.M_SKILL='"+this.TextBox3.Text.Trim()+"'or b.M_TYPE='"+this.TextBox3.Text.Trim()+"'";
            }            //根据语言查询
            if (this.Languageddl.SelectedValue!="")
            {
                ssql += " and c.LANGUAGE='"+this.Languageddl.DataValueField+"'";
            }
            
            //根据职称查询
            if (this.Techposddl.SelectedValue != "")
            {
                ssql += " and a.TECHPOS='"+this.Techposddl.DataValueField+"'";
            }
            if (this.Deptddl.SelectedValue != "")
            {
                ssql += " and a.DEPT='"+this.Deptddl.DataValueField+"'";
            }  
            //GridView1.DataSourceID = "SqlDataSource1";
            this.SqlDataSource1.SelectCommand = ssql;
            this.DataBind();
 
        }你好像还没有加表之间的关联

Answer 2

改 ssql += " from D_STAFF_BASE a,D_SKILL_VIEW b,D_STAFF_LANG_ABILITY c where 1=1";
然后
 //根据姓名查询
            if (this.TextBox1.Text.Trim() != "")
            {
               
                ssql += " and a.CNNAME='"+this.TextBox1.Text.Trim()+"'";
            }
后面的都将“Where”改为“and”

Answer 3

在
this.SqlDataSource1.SelectCommand = ssql;
之前，把ssql打印出来或者单步调试一下，看是什么SQL语句，然后放到数据库里执行一次，看报什么错，那就什么都明白了。ps,功底有待于加强，这种错误应该很容易排除的。  
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Answer 4

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