Query Data

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FreeSql has made great efforts in querying data, especially the functions such as chain query syntax, multi-table query, expression function, etc.

• 《Paging Query》
• 《Query from Single Table》
• 《Query from Multi-table》
• 《Grouped Aggregate Query》
• 《Return Data》
• 《LinqToSql》
• 《Repository Layer》
• 《Filters and Global Filters》
• 《FreeSql Optimization: Lazy Loading》
• 《FreeSql Optimization: Greed Loading》
• 《Expression Function》
• 《Using Read/Write Separation》
• 《Performance》
• 《Sharding Tables and Database》
• 《Tenant》

Special introduction to WhereDynamicFilter

The ISelect.WhereDynamicFilter method implements dynamic filter conditions (interacting with the front-end), supported operators:

• Contains/StartsWith/EndsWith/NotContains/NotStartsWith/NotEndsWith: include/not include, like'%xx%', or like'xx%', or like'%xx'
• Equal/NotEqual
• GreaterThan/GreaterThanOrEqual
• LessThan/LessThanOrEqual
• Range: Range query
• DateRange: date range, with special processing value[1] + 1
• Any/NotAny: Does it match any item in value (to put it bluntly, SQL IN)

DynamicFilterInfo dyfilter = JsonConvert.DeserializeObject<DynamicFilterInfo>(@"
{
  ""Logic"" : ""Or"",
  ""Filters"" :
  [
    {
      ""Field"" : ""Code"", ""Operator"" : ""NotContains"", ""Value"" : ""val1"", 
      ""Filters"" : [{ ""Field"" : ""Name"", ""Operator"" : ""NotStartsWith"", ""Value"" : ""val2"" }]
    },
    {
      ""Field"" : ""Parent.Code"", ""Operator"" : ""Equals"", ""Value"" : ""val11"",
      ""Filters"" : [{ ""Field"" : ""Parent.Name"", ""Operator"" : ""Contains"", ""Value"" : ""val22"" }]
    }
  ]
}");
fsql.Select<VM_District_Parent>().WhereDynamicFilter(dyfilter).ToList();
//SELECT a.""Code"", a.""Name"", a.""ParentCode"", a__Parent.""Code"" as4, a__Parent.""Name"" as5, a__Parent.""ParentCode"" as6 
//FROM ""D_District"" a 
//LEFT JOIN ""D_District"" a__Parent ON a__Parent.""Code"" = a.""ParentCode"" 
//WHERE (not((a.""Code"") LIKE '%val1%') AND not((a.""Name"") LIKE 'val2%') OR a__Parent.""Code"" = 'val11' AND (a__Parent.""Name"") LIKE '%val22%')

Dynamic sorting: ISelect.OrderByPropertyName("Parent.Code")

API

Methods	Return	Parameters	Description
ToSql	string		Return the SQL statement to be executed
ToList	List<T1>		执行SQL查询，返回 T1 实体所有字段的记录，若存在导航属性则一起查询返回，记录不存在时返回 Count 为 0 的列表
ToList<T>	List<T>	Lambda	执行SQL查询，返回指定字段的记录，记录不存在时返回 Count 为 0 的列表
ToList<T>	List<T>	string field	执行SQL查询，返回 field 指定字段的记录，并以元组或基础类型(int,string,long)接收，记录不存在时返回 Count 为 0 的列表
ToOne	T1		执行SQL查询，返回 T1 实体所有字段的第一条记录，记录不存在时返回 null
ToAggregate<T>	List<T>	Lambda	执行SQL查询，返回指定字段的聚合结果（适合不需要 GroupBy 的场景）
Any	bool		Execute SQL query, if there are records, return true, otherwise return false.
Sum	T	Lambda	Specify a column and calculate the sum.
Min	T	Lambda	Specify a column and calculate the minimum value.
Max	T	Lambda	Specify a column and calculate the maximum value.
Avg	T	Lambda	Specify a column, calculate the average value.
【Pagination】
Count	long		The number of queried records
Count	<this>	out long	The number of queried records, returned in the form of parameter out
Skip	<this>	int offset	Query the number of rows shifted backward
Offset	<this>	int offset	Query the number of rows shifted backward
Limit	<this>	int limit	Query a specified amount of data
Take	<this>	int limit	Query a specified amount of data
Page	<this>	int pageIndex, int pageSize	Pagination
【Where】
Where	<this>	Lambda	Supports multi-table query expressions, multiple use is equivalent to AND.
WhereIf	<this>	bool, Lambda	Support multi-table query expression
Where	<this>	string, parms	Native Sql syntax conditions, Where("id = @id", new {id = 1 }) Note that the prefix @ will be determined according to the specific database
WhereIf	<this>	bool, string, parms	Native Sql syntax conditions, WhereIf(true, "id = @id", new {id = 1 }) Note that the prefix @ will be determined according to the specific database
WhereCascade	<this>	Lambda	When querying multiple tables, add conditions to each table.
WhereDynamicFilter	<this>	DynamicFilterInfo	Dynamic filter conditions (interact with the front end)
【Group】
GroupBy	<this>	Lambda	按选择的列分组，GroupBy(a => a.Name)
GroupBy	<this>	string, parms	按原生sql语法分组，GroupBy("concat(name, @cc)", new { cc = 1 }) ，注意前缀@，根据具体数据库决定
Having	<this>	string, parms	按原生sql语法聚合条件过滤，Having("count(name) = @cc", new { cc = 1 })，注意前缀@，根据具体数据库决定
Distinct	<this>		.Distinct().ToList(x => x.GroupName) 是对指定字段
【Order】
OrderBy	<this>	Lambda	按列排序，OrderBy(a => a.Time)，可多次使用
OrderByDescending	<this>	Lambda	按列倒向排序，OrderByDescending(a => a.Time)
OrderBy	<this>	string, parms	按原生sql语法排序，OrderBy("count(name) + @cc", new { cc = 1 })
OrderByPropertyName	string, bool	按属性名字符串排序（支持导航属性）
【Join】
LeftJoin	<this>	Lambda	左联查询，可使用导航属性，或指定关联的实体类型
InnerJoin	<this>	Lambda	联接查询，可使用导航属性，或指定关联的实体类型
RightJoin	<this>	Lambda	右联查询，可使用导航属性，或指定关联的实体类型
LeftJoin	<this>	string, parms	左联查询，使用原生sql语法，LeftJoin("type b on b.id = a.id and b.clicks > @clicks", new { clicks = 1 })
InnerJoin	<this>	string, parms	联接查询，使用原生sql语法，InnerJoin("type b on b.id = a.id and b.clicks > @clicks", new { clicks = 1 })
RightJoin	<this>	string, parms	右联查询，使用原生sql语法，RightJoin("type b on b.id = a.id and b.clicks > @clicks", new { clicks = 1 })
From	<this>	Lambda	多表查询，3个表以上使用非常方便，目前设计最大支持10个表
【Other】
As	<this>	string alias = "a"	指定别名
Master	<this>		指定从主库查询（默认查询从库）
CommandTimeout	<this>	int	命令超时设置(秒)
WithTransaction	<this>	DbTransaction	设置事务对象
WithConnection	<this>	DbConnection	设置连接对象
WithLock	<this>	Enum	SqlServer NoLock 等特有的设置
ForUpdate	<this>	bool	排他更新锁，对不同的数据库已作适配，详细说明见注释
AsQueryable	IQueryable		将 ISelect 转换为 IQueryable，此方法主要用于扩展，比如：abp IRepository GetAll() 接口方法需要返回 IQueryable 对象。注意：IQueryable 方法污染较为严重，请尽量避免此转换
InsertInto	int	string, Lambda	将查询转换为 INSERT INTO tableName SELECT ... FROM t 执行插入
ToUpdate	IUpdate<TENtity>	无	将查询转为更新对象
ToDelete	IDelete<TENtity>	无	将查询转为删除对象
ToTreeList	List<TEntity>	无	将父子关系的数据以 TreeList 的形式返回
AsTreeCte	ISelect	(up, pathSelector, level)	递归查询父子关系表