SQL Server 游标生成工具 技术原理和源代码分享

经常做ERP报表，涉及存储过程中读取数据，多个表之间关联的数据读取，用到游标。经典的读取用户表的游标例子

Declare @Age int
Declare @Name varchar(20)
Declare Cur Cursor For Select Age,Name From T_User   
Open Cur
Fetch next From Cur Into @Age,@Name
While @@fetch_status=0     
Begin
   Update T_User Set [Name]=@Name,Age=@Age
   Fetch Next From Cur Into @Age,@Name
End   
Close Cur   
Deallocate Cur

在实际应用时，经常需要找到这个模板，然后再根据实际的表结果，重写一遍。经常遇到以下二个问题

1  上面的例子脚本不知道放在哪里了，或是有很多例子脚本，不方便很快找出来

2  重写游标的例子，经常重复，又没有技术难度可言。比如读取工作单生产计划，读取用户。

经过思考，于是写个游标生成工具，把上面的模板代码，应用到代码生成器中。

注意上图中的Script Cursor，这是用来生成游标模板的。选择一个数据库，树左边选择表名，勾选字段值，点击执行

 DECLARE  @UserID  NVARCHAR(10) 
 DECLARE  @UserName  NVARCHAR(50) 
 DECLARE  Cur  CURSOR  FOR  SELECT  [UserID],[UserName]  FROM  [USER]   
 OPEN  Cur 
 FETCH  next  FROM  Cur  INTO  @UserID,@UserName   
 WHILE  @@fetch_status=0         
 BEGIN 
     FETCH  next  FROM  Cur  INTO  @UserID,@UserName   
 END       
 CLOSE  Cur       
 DEALLOCATE  Cur 

源代码不到50行，全文如下

 List<ColumnInfo>  fieldlist = this.GetFieldlist();
 StringBuilder builder=new StringBuilder();
 string typeName = string.Empty;
           
 foreach (ColumnInfo columnInfo in fieldlist)
    {
                switch (columnInfo.TypeName)
                {
                    case "datetime":
                    case "int":
                    case "image":
                    case "bit":
                        typeName = columnInfo.TypeName;
                        break;
                    case "nvarchar":
                    case "nchar":
                    case "varchar":
                    case "char":
                        typeName =string.Format("{0}({1})", columnInfo.TypeName,columnInfo.Length);
                        break;
                }
                builder.AppendLine(string.Format("Declare @{0} {1}", columnInfo.ColumnName, typeName));
  }
var columns = string.Join(",", (from column in fieldlist
                                            select "["+column.ColumnName+"]").ToArray());

string fetchNex= string.Join(",", (from column in fieldlist
                                            select "@"+column.ColumnName).ToArray());

string update= string.Join(",", (from column in fieldlist
                                              select "@"+column.ColumnName+"=["+ column.ColumnName+"]").ToArray());

builder.AppendLine(string.Format("Declare Cur Cursor For Select {0} From [{1}] ", columns, this.tablename));
builder.AppendLine("Open Cur");
 builder.AppendLine(string.Format("Fetch next From Cur Into {0} ", fetchNex));
 builder.AppendLine("While @@fetch_status=0    ");
 builder.AppendLine("Begin");
            
//builder.AppendLine(string.Format("  Update [{0}] Set {1} ",this.tablename,update));
builder.AppendLine(string.Format("  Fetch next From Cur Into {0} ", fetchNex));

builder.AppendLine("End   ");
builder.AppendLine("Close Cur   ");
builder.AppendLine("Deallocate Cur");

有以下几点需要注意

1  生成的脚本中，字段名称，表名称，均要加上方括号，以避免名称重突。

2  最后生成的SQL源代码，还需要应用下面的方法，将SQL关键字大写。

将SQL查询语句的关键字大写的方法来自CSDN下载区，全文如下

 private static Regex RegexSQLCapitalize = new Regex("\\badd\\b|\\baggregate\\b|\\baction\\b|\\balter\\b|\\bas\\b|\\basc\\b|\\basymmetric\\b|\\bauthorization\\b|\\bbegin\\b|\\bbinary\\b|\\bbit\\b|\\bby\\b|\\bcascade\\b|\\bcase\\b|\\bcatalog\\b|\\bcharacter\\b|\\bchar\\b|\\bcheck\\b|\\bcheckpoint\\b|\\bclose\\b|\\bclustered\\b|\\bconstraint\\b|\\bcollate\\b|\\bcolumn\\b|\\bcommit\\b|\\bcontains\\b|\\bcontinue\\b|\\bcreate\\b|\\bcross\\b|\\bcursor\\b|\\bdatabase\\b|\\bdeallocate\\b|\\bdesc\\b|\\bdecimal\\b|\\bdeclare\\b|\\bdefault\\b|\\bdelete\\b|\\bdesc\\b|\\bdistinct\\b|\\bdouble\\b|\\bdrop\\b|\\belse\\b|\\bend\\b|\\bescape\\b|\\bexcept\\b|\\bexec\\b|\\bexecute\\b|\\bexternal\\b|\\bfetch\\b|\\bfloat\\b|\\bforeign\\b|\\bfor\\b|\\bfrom\\b|\\bfunction\\b|\\bget\\b|\\bgroup\\b|\\bgoto\\b|\\bgrant\\b|\\bhaving\\b|\\bidentity\\b|\\binto\\b|\\bindex\\b|\\binsert\\b|\\binstead\\b|\\bint\\b|\\bkey\\b|\\bname\\b|\\bof\\b|\\bon\\b|\\bopen\\b|\\boption\\b|\\border\\b|\\boutput\\b|\\bprimary\\b|\\breturn\\b|\\brollback\\b|\\bschema\\b|\\bselect\\b|\\bsize\\b|\\bsymmetric\\b|\\bset\\b|\\bserver\\b|(\\btable\\b)|\\bthen\\b|\\btop\\b|\\btime\\b|\\btimestamp\\b|\\bto\\b|\\btrigger\\b|\\bprocedure\\b|\\btype\\b|\\bunion\\b|\\bunique\\b|\\bupdate\\b|\\buse\\b|\\bvalues\\b|\\bvalue\\b|\\bvarchar\\b|\\bview\\b|\\bwhen\\b|\\bwhile\\b|\\bwhere\\b|\\bwith\\b|\\bnvarchar\\b|\\bnchar\\b|\\bdatetime\\b|\\bfloat\\b|\\bdate\\b|\\bdatediff\\b|\\bdateadd\\b|\\bdatename\\b|\\bdatepart\\b|getdate|\\breferences\\b|\\babs\\b|\\bavg\\b|\\bcast\\b|\\bconvert\\b|\\bcount\\b|\\bday\\b|\\bisnull\\b|\\blen\\b|\\bmax\\b|\\bmin\\b|\\bmonth\\b|\\byear\\b|\\breplace\\b|\\bsubstring\\b|\\bsum\\b|\\bupper\\b|\\buser\\b|\\ball\\b|\\bany\\b|\\band\\b|\\bbetween\\b|\\bexists\\b|\\bin\\b|\\binner\\b|\\bis\\b|\\bjoin\\b|\\bleft\\b|\\blike\\b|\\bnot\\b|\\bnull\\b|\\bor\\b|\\bright\\b|\\btry\\b|\\bcatch\\b", RegexOptions.IgnoreCase);

 public static string CapitalizeSQLClause(string source)
 {

            //先按行划分
            Regex rowReg = new Regex("\r\n");
            string[] strRows = rowReg.Split(source);

            StringBuilder strBuilder = new StringBuilder();
            int rowsCount = strRows.Length;

            for (int i = 0; i < rowsCount; i++)
            {
                //去掉一行中的一个或多个空白
                //strRows[i] = Regex.Replace(strRows[i], @"\s+", " ");

                //按空格划分
                string[] strWords = strRows[i].Split(new char['\0']);
                int wordsCount = strWords.Length;

                for (int j = 0; j < wordsCount; j++)
                {
                    strBuilder.Append(" ");
                    if (RegexSQLCapitalize.IsMatch(strWords[j]))
                    {

                        MatchCollection mc = RegexSQLCapitalize.Matches(strWords[j]);
                        int mcCount = mc.Count;
                        for (int k = 0; k < mcCount; k++)
                        {
                            strWords[j] = strWords[j].Replace(mc[k].Value, mc[k].Value.ToUpper());
                        }
                        strBuilder.Append(strWords[j]);
                    }
                    else
                    {
                        strBuilder.Append(strWords[j]);
                    }
                    strBuilder.Append(" ");
                }

                strBuilder.Append("\r\n");
            }
            return strBuilder.ToString().Replace("\r\n\r\n", "\r\n");
 }

正则表达式替换字符串中的关键字，这个方法没有任何依赖，可拷贝到您的项目或类库中，为SQL 脚本增加关键字大写功能。

3  SQL 脚本格式化功能  如果能把生成的SQL脚本格式化一下，生成美观的SQL脚本，增加可读性。SQL Pretty Printer可以做到，但是没有找到API可以调用这个功能。

4 多表关联的游标模板没有做到。应该尝试从多个关联表中生成游标。不过表与表之间的关系难以自动生成，比如像下面的母子表游标询语句

Declare Cur Cursor For Select r.Description,r.WorkCenter  FROM JobOrder  j, JobOrderRouting r
     WHERE j.JobNo=r.JobNo
Open Cur

游标要从2个关联的表中读取数据，如果2个表之间有外键关联，可以生成2个表的外键关联字段的关系，也就是上面的SQL游标可以自动生成，但是有的2个表之间没有外键关联的，还是要手工指定，相当于是个半成品的游标生成器，于是只好把这个功能点拿掉，只做最简单的一种情况，生成一个表的若干个字段的游标查询，没有设计多表查询的游标。