ServiceStack.OrmLite 笔记10-group having 分页orderby等

group having 分页等

var ev = OrmLiteConfig.DialectProvider.SqlExpression();

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group的使用
同sql一样，注意group分组的字段要在select里

ev.Select(c => new { c.Birthday, c.Active }).Where(rn => rn.Birthday >= new DateTime(year, 1, 1) && rn.Birthday <= lastDay).GroupBy(rn => new { rn.Birthday,rn.Active});

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having的使用

ev.Select(c => new { c.Birthday, c.Active }).Where(rn => rn.Birthday >= new DateTime(year, 1, 1) && rn.Birthday <= lastDay).GroupBy(rn => new { rn.Birthday, rn.Active }).Having(x=>Sql.Max(x.Rate)>5);

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orderby 排序
一升一降 先降后升 ordered by Rate Descending and Name Ascending
ev.Where().OrderBy(rn => new { at = Sql.Desc(rn.Rate), rn.Name })
也可以用这个OrderByDescending

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Limit 分页
其实就是skip 然后take
ev.Limit(5); 默认是take 即top 5
ev.Limit(0, 4);// first page, page size=4;
ev.Limit(4, 4);// second page
ev.Limit().OrderBy(); // clear limit, clear orde

 ToCountStatement 总数
  var expr = db.From<LetterFrequency>() .Join<LetterFrequency, LetterStat>() .Where<LetterStat>(x => x.Id > 0);

var rscount= expr.ToCountStatement();//获取expr表达式结果的总数

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 ev.SelectDistinct(r => r.City);
 ev.Select(r => Sql.As(Sql.Max(r.Birthday), "Birthday")); //列别名Birthday
 var r2 = db.Scalar<Author, DateTime>(e => Sql.Max(e.Birthday));Author表 DateTime类型

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联接
LeftJoin

db.Column < string > ( db.From < TableA > ()
.LeftJoin < TableB >((a, b) => a.Id == b.Id)
.Where < TableB > (b => b.Id == null)
.Select(a => a.Name));

Join

db.From < TableA > ()
.Join < TableB > ()
.OrderBy(x => x.Id);

CrossJoin

db.From < CrossJoinTableA > ()
.CrossJoin < CrossJoinTableB >()
.OrderBy < CrossJoinTableA >(x => x.Id)
.ThenBy < CrossJoinTableB >(x => x.Id);

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调试

db.GetLastSql().Print();