SQLJoinTableBuilder有一个Union方法，可以组合多个其他SQLJoinTableBuilder的查询结果。

语法：

Union(Builder, All)

Builder：被组合的另一个SQLJoinTableBuilder
All：  可选参数，组合的时候默认是排除重复值的，如果需要组合所有数据，请将此参数设置为True

参与组合的多个SQLJoinTableBuilder，其生成的查询表必须具备相同的结构。

示例

假设你有订单2009、订单2010、订单2011三个表，需要从这三个订单表中找出所有客户为“红阳事业”的订单：

Dim jb1 As New SQLJoinTableBuilder("查询表1","订单2009")
jb1.ConnectionName = "Sale"
jb1.AddTable("订单","产品ID","产品","产品ID")
jb1.AddTable("订单", "客户ID","客户","客户ID")
jb1.AddCols("产品名称","客户名称","日期", "数量","单价")
jb1.AddExp("金额","数量 * 单价")
jb1.Filter = "客户名称 = '红阳事业'" 

Dim jb2 As New SQLJoinTableBuilder("查询表1","订单2010")
jb2.ConnectionName = "Sale"
jb2.AddTable("订单","产品ID","产品","产品ID")
jb2.AddTable("订单", "客户ID","客户","客户ID")
jb2.AddCols("产品名称","客户名称","日期", "数量","单价")
jb2.AddExp("金额","数量 * 单价")
jb2.Filter = "客户名称 = '红阳事业'"

Dim jb3 As New SQLJoinTableBuilder("查询表1","订单2011")
jb3.ConnectionName = "Sale"
jb3.AddTable("订单","产品ID","产品","产品ID")
jb3.AddTable("订单", "客户ID","客户","客户ID")
jb3.AddCols("产品名称","客户名称","日期", "数量","单价")
jb3.AddExp("金额","数量 * 单价")
jb3.Filter = "客户名称 = '红阳事业'"

jb1.Union(jb2) '组合jb2
jb1.Union(jb3) '组合jb3
jb1.Build()

MainTable = Tables("查询表1")

组合不同数据源的查询结果

如果查询结果来自于不同的数据源，需要采用Merge方法组合，Merge方法不如Union方法高效。

示例

假设你有三个数据源，分别为Sale1、Sale2、Sale3，三个数据源都有订单表，需要从这三个订单表中找出所有客户为“红阳事业”的订单：

Dim jb1 As New SQLJoinTableBuilder("查询表1","订单")
jb1.ConnectionName = "Sale1"
jb1.AddTable("订单","产品ID","产品","产品ID")
jb1.AddTable("订单", "客户ID","客户","客户ID")
jb1.AddCols("产品名称","客户名称","日期", "数量","单价")
jb1.AddExp("金额","数量 * 单价")
jb1.Filter = "客户名称 = '红阳事业'" 

Dim jb2 As New SQLJoinTableBuilder("查询表1","订单")
jb2.ConnectionName = "Sale2"
jb2.AddTable("订单","产品ID","产品","产品ID")
jb2.AddTable("订单", "客户ID","客户","客户ID")
jb2.AddCols("产品名称","客户名称","日期", "数量","单价")
jb2.AddExp("金额","数量 * 单价")
jb2.Filter = "客户名称 = '红阳事业'"

Dim jb3 As New SQLJoinTableBuilder("查询表1","订单")
jb3.ConnectionName = "Sale3"
jb3.AddTable("订单","产品ID","产品","产品ID")
jb3.AddTable("订单", "客户ID","客户","客户ID")
jb3.AddCols("产品名称","客户名称","日期", "数量","单价")
jb3.AddExp("金额","数量 * 单价")
jb3.Filter = "客户名称 = '红阳事业'" 

jb1.Merge(jb2) '组合jb2
jb1.Merge(jb3) '组合jb3
jb1.Build()

MainTable = Tables("查询表1")