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Created With Sql (markdown)
AlexLEWIS
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With-Sql.md
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With-Sql.md
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[中文](withsql) | **English**
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# WithSql 自定义SQL
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定义实体类
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```csharp
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public class TestClass
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{
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[Column(Name = "ID", IsPrimary = true)]
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public string No { get; set; }
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public int? Age { get; set; }
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public string Name { get; set; }
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[Column(Name = "BIRTH_DAY")]
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public DateTime? Birthday { get; set; }
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public decimal Point { get; set; }
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public Sex? Sex { get; set; }
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}
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public class TestClssDto
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{
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public string ID { get; set; }
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public int? Age { get; set; }
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}
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```
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不同的查询方式。
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- 返回`DataTable`
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- 返回`List<Tuplue>` 即`List<(string,string)>`元组
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- 返回`List<object>` 且能支持分页
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- 返回`List<TestClassDto>`且能支持分页
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### 1.返回DataTable
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```csharp
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DataTable dt1 = _fsql.Select<object>()
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.WithSql("select * from TestClass ")
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.ToDataTable("ID,Age");
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```
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```sql
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SELECT ID,Age
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FROM(select * from TestClass ) a
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```
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### 2.返回DataTable
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```csharp
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DataTable dt2 = _fsql.Select<object>()
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.WithSql("select * from TestClass ")
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.ToDataTable("*");
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```
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```sql
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SELECT *
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FROM ( select * from TestClass ) a
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```
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### 3.返回`List<Tuplue>` 即`List<(string,string)>` 元组
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```csharp
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List<(string,string)> list1 = _fsql
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.Select<object>()
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.WithSql("select * from TestClass ")
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.ToList<(string, string)>("ID,Age");
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```
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```sql
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SELECT ID, Age
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FROM(select * from TestClass ) a
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```
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### 4.返回`List<object>`
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```csharp
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var list2 = _fsql.Select<object>()
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.WithSql("select * from TestClass ")
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.ToList<object>("*");
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```
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```sql
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SELECT *
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FROM(select * from TestClass ) a
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```
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### 5.返回`List<object>` 且能支持分页
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```csharp
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var list3 = _fsql.Select<object>()
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.WithSql("select * from TestClass ")
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.WhereIf(true, "1=1")
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.Page(1, 10).OrderBy("ID DESC")
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.ToList<object>("ID,Age");
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```
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```sql
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SELECT ID, Age
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FROM(select * from TestClass ) a
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WHERE(1 = 1)
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ORDER BY ID DESC
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limit 0,10
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```
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### 6.返回`List<TestClassDto>`且能支持分页
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```csharp
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var list4 = _fsql.Select<object>()
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.WithSql("select * from TestClass ")
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.WhereIf(true, "1=1")
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.Page(1, 10)
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.OrderBy("ID DESC")
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.ToList<TestClssDto>("ID,Age");
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```
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```sql
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SELECT ID, Age
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FROM(select * from TestClass ) a
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WHERE(1 = 1)
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ORDER BY ID DESC
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limit 0,10
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```
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## 通过 WithSql+ ToSQL实现 Union ALL 查询方法
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### 1、二次 ISelect 查询：WithSql 使用多次，等于 UNION ALL 查询
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WithSql 使用多次为 UNION ALL 查询，所以我们可以利用 ISelect.ToSql(FieldAliasOptions.AsProperty) 得到生成的 SQL，如下：
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```csharp
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var sql1 = fsql.Select<Topic>()
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.Where(a => a.Title.Contains("xxx"))
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.ToSql();
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var sql2 = fsql.Select<Topic>()
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.Where(a => a.Title.Contains("yyy"))
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.ToSql();
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fsql.Select<Topic>()
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.WithSql(sql1)
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.WithSql(sql2)
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.ToList();
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```
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```sql
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SELECT * from (SELECT a.`Id`, a.`Clicks`, a.`TypeGuid`, a.`Title`, a.`CreateTime`
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FROM ( SELECT a.`Id`, a.`Clicks`, a.`TypeGuid`, a.`Title`, a.`CreateTime`
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FROM `tb_topic` a
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WHERE ((a.`Title`) LIKE '%xxx%') ) a) ftb
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UNION ALL
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SELECT * from (SELECT a.`Id`, a.`Clicks`, a.`TypeGuid`, a.`Title`, a.`CreateTime`
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FROM ( SELECT a.`Id`, a.`Clicks`, a.`TypeGuid`, a.`Title`, a.`CreateTime`
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FROM `tb_topic` a
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WHERE ((a.`Title`) LIKE '%yyy%') ) a) ftb
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```
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### 2、跨分表查询：AsTable 相同实体多次操作，等于 Union ALL 查询
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```c#
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var sql = fsql.Select<User>()
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.AsTable((type, oldname) => "table_1")a
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.AsTable((type, oldname) => "table_2")
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.ToSql(a => a.Id);
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```
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```sql
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select * from (SELECT a."Id" as1 FROM "table_1" a) ftb
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UNION ALL
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select * from (SELECT a."Id" as1 FROM "table_2" a) ftb
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```
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### 3、利用 ToSql 拼接新的 SQL，使用 IAdo 执行
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```c#
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var sql1 = fsql.Select<Topic>()
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.Where(a => a.Id > 100 && a.Id < 200)
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.ToSql(a => new { a.Id, a.Title }, FieldAliasOptions.AsProperty);
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var sql2 = fsql.Select<Topic>()
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.Where(a => a.Id > 1001 && a.Id < 1200)
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.ToSql(a => new { a.Id, a.Title }, FieldAliasOptions.AsProperty);
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fsql.Ado.CommandFluent($"{sql1} UNION ALL {sql2}")
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.ExecuteDataTable();
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```
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## 分页问题
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Union All 之后 如果直接 分页会有一个问题。请看具体示例
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### 多次WithSql+Page存在问题：每个WithSql内都有一个Page分页
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```csharp
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var sql1 = fsql.Select<Topic>()
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.Where(a => a.Title.Contains("xxx"))
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.ToSql();
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var sql2 = fsql.Select<Topic>()
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.Where(a => a.Title.Contains("yyy"))
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.ToSql();
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fsql.Select<Topic>().WithSql(sql1).WithSql(sql2).Page(1, 20).ToList();
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```
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```sql
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SELECT * from (SELECT a.`Id`, a.`Clicks`, a.`TypeGuid`, a.`Title`, a.`CreateTime`
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FROM ( SELECT a.`Id`, a.`Clicks`, a.`TypeGuid`, a.`Title`, a.`CreateTime`
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FROM `tb_topic` a
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WHERE ((a.`Title`) LIKE '%xxx%') ) a
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limit 0,20) ftb
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UNION ALL
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SELECT * from (SELECT a.`Id`, a.`Clicks`, a.`TypeGuid`, a.`Title`, a.`CreateTime`
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FROM ( SELECT a.`Id`, a.`Clicks`, a.`TypeGuid`, a.`Title`, a.`CreateTime`
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FROM `tb_topic` a
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WHERE ((a.`Title`) LIKE '%yyy%') ) a
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limit 0,20) ftb
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```
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多个sql union all使用withsql，直接Page分页，会导致每个子表都生效，子表都生成分页。
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WithSql 可以和 AsTable 实现分表的功能。
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分表跨表查询的时候，分页是要向每个子表（即每个WithSql中的SQL分页）都生效。
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## Solution
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### Call WithSql Multiple Times
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Call WithSql multiple times. If you need to paging, you need to follow the two steps below.
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- Step 1: combine the two Sql statements into one by `WithSql`:
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```csharp
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var sql = fsql.Select<Topic>()
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.WithSql("SELECT * FROM tb_topic where id > 11")
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.WithSql("SELECT * FROM tb_topic where id < 10")
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.ToSql("*")
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```
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The above code will be generated as a Sql statement using `UNION ALL`:
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```sql
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SELECT * from (SELECT *
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FROM ( SELECT * FROM tb_topic where id > 11 ) a) ftb
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UNION ALL
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SELECT * from (SELECT *
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FROM ( SELECT * FROM tb_topic where id < 10 ) a) ftb
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```
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- Step 2: on the basis of the SQL statement containing `UNION ALL`, page by calling the `Page` method:
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```csharp
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var sql2 = g.mysql.Select<Topic>()
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.WithSql(sql)
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.Page(2, 10)
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.ToSql();
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```
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```sql
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SELECT a.`Id`, a.`Clicks`, a.`TypeGuid`, a.`Title`, a.`CreateTime`
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FROM ( SELECT * from (SELECT *
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FROM ( SELECT * FROM tb_topic where id > 11 ) a) ftb
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UNION ALL
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SELECT * from (SELECT *
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FROM ( SELECT * FROM tb_topic where id < 10 ) a) ftb ) a
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limit 10,10
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```
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