diff --git a/build.gradle b/build.gradle
index e99a089..76d13db 100644
--- a/build.gradle
+++ b/build.gradle
@@ -58,6 +58,7 @@ subprojects {
         }
         mavenCentral()
         mavenLocal()
+        jcenter()
     }
     dependencies {
         compile(
@@ -143,6 +144,7 @@ project(':core') {
                 "org.postgresql:postgresql:$postgresVersion",
                 "mysql:mysql-connector-java:$mysqlVersion",
                 "org.xerial:sqlite-jdbc:3.8.11.2",
+                "org.amshove.kluent:kluent:1.47"
         )
     }
 }
diff --git a/core/out/test/resources/logback.xml b/core/out/test/resources/logback.xml
new file mode 100644
index 0000000..ffe6a3e
--- /dev/null
+++ b/core/out/test/resources/logback.xml
@@ -0,0 +1,35 @@
+<!--
+  ~ Copyright (c) 2015 Andrew O'Malley
+  ~
+  ~ Permission is hereby granted, free of charge, to any person obtaining a copy
+  ~ of this software and associated documentation files (the "Software"), to deal
+  ~ in the Software without restriction, including without limitation the rights
+  ~ to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+  ~ copies of the Software, and to permit persons to whom the Software is
+  ~ furnished to do so, subject to the following conditions:
+  ~
+  ~ The above copyright notice and this permission notice shall be included in
+  ~ all copies or substantial portions of the Software.
+  ~
+  ~ THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+  ~ IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+  ~ FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+  ~ AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+  ~ LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+  ~ OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+  ~ THE SOFTWARE.
+  -->
+
+<configuration>
+    <appender name="console" class="ch.qos.logback.core.ConsoleAppender">
+        <encoder>
+            <pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n</pattern>
+        </encoder>
+    </appender>
+
+    <root level="debug">
+        <appender-ref ref="console"/>
+    </root>
+
+    <logger name="com.github.andrewoma.kwery.core.interceptor.LoggingInterceptor" level="debug"/>
+</configuration>
\ No newline at end of file
diff --git a/core/src/main/kotlin/com/github/andrewoma/kwery/core/builder/Join.kt b/core/src/main/kotlin/com/github/andrewoma/kwery/core/builder/Join.kt
new file mode 100644
index 0000000..c4b774d
--- /dev/null
+++ b/core/src/main/kotlin/com/github/andrewoma/kwery/core/builder/Join.kt
@@ -0,0 +1,27 @@
+package com.github.andrewoma.kwery.core.builder
+
+data class Join(
+    val type: Type,
+    val table: String,
+    val handler: String = table.split("_").map { it.first().toLowerCase() }.joinToString(""),
+    val andClauses: MutableList<(String) -> String> = mutableListOf(),
+    val builder: Join.(String) -> String
+) {
+
+    enum class Type(val value: String) {
+        Inner("inner"),
+        Left("left"),
+        Right("right")
+    }
+
+    infix fun and(clause: (handler: String) -> String) = apply { andClauses.add(clause) }
+
+    val on = builder(this, handler)
+
+    fun on(clause: String) = clause
+
+    fun getSql(): String {
+        val and = andClauses.joinToString(" ") { "and ${it(handler)}" }
+        return "${type.value} join $table $handler on $on $and".trim()
+    }
+}
diff --git a/core/src/main/kotlin/com/github/andrewoma/kwery/core/builder/JoinGroup.kt b/core/src/main/kotlin/com/github/andrewoma/kwery/core/builder/JoinGroup.kt
new file mode 100644
index 0000000..d92a1b0
--- /dev/null
+++ b/core/src/main/kotlin/com/github/andrewoma/kwery/core/builder/JoinGroup.kt
@@ -0,0 +1,39 @@
+package com.github.andrewoma.kwery.core.builder
+
+import com.github.andrewoma.kwery.core.builder.Join.Type.*
+
+class JoinGroup(internal val builders: MutableList<JoinGroup.() -> Unit> = mutableListOf()) {
+
+    private var counter = 0
+    private val joins = mutableMapOf<Int, Join>()
+    private val literalJoins = mutableMapOf<Int, String>()
+
+    internal fun addBuilder(builder: JoinGroup.() -> Unit) = builders.add(builder)
+
+    fun Join.add(): Join = if (joins.any { it.value.handler == handler }) {
+        copy(handler = this.handler + "1").add()
+    } else this.also { joins[counter++] = it }
+
+    fun innerJoin(table: String, handler: String? = null, builder: Join.(String) -> String) =
+        join(Inner, table, handler, builder)
+
+    fun leftJoin(table: String, handler: String? = null, builder: Join.(String) -> String) =
+        join(Left, table, handler, builder)
+
+    fun rightJoin(table: String, handler: String? = null, builder: Join.(String) -> String) =
+        join(Right, table, handler, builder)
+
+    fun join(sql: String) = literalJoins.put(counter++, sql)
+
+    fun join(type: Join.Type, table: String, handler: String?, builder: Join.(String) -> String): Join {
+        val join = handler?.let { Join(type, table, it, builder = builder) }
+                ?: Join(type, table, builder = builder)
+        return join.add()
+    }
+
+    fun build(): String {
+        builders.forEach { it(this) }
+        val joins = (literalJoins + joins.mapValues { it.value.getSql() }).toSortedMap()
+        return joins.values.joinToString("\n")
+    }
+}
diff --git a/core/src/main/kotlin/com/github/andrewoma/kwery/core/builder/Query.kt b/core/src/main/kotlin/com/github/andrewoma/kwery/core/builder/Query.kt
index 764507b..eb78a06 100644
--- a/core/src/main/kotlin/com/github/andrewoma/kwery/core/builder/Query.kt
+++ b/core/src/main/kotlin/com/github/andrewoma/kwery/core/builder/Query.kt
@@ -22,6 +22,14 @@
 
 package com.github.andrewoma.kwery.core.builder
 
-class Query(val sqlBuffer: StringBuilder, val parameters: Map<String, Any?>) {
+class Query(private val sqlBuffer: StringBuilder, val parameters: Map<String, Any?>) {
     val sql: String by lazy { sqlBuffer.toString() }
-}
\ No newline at end of file
+
+    private fun union(kQuery: Query, unionType: String) = Query(
+        StringBuilder("$sql $unionType ${kQuery.sql}"),
+        parameters + kQuery.parameters
+    )
+
+    infix fun union(kQuery: Query) = union(kQuery, unionType = "UNION")
+    infix fun unionAll(kQuery: Query) = union(kQuery, unionType = "UNION ALL")
+}
diff --git a/core/src/main/kotlin/com/github/andrewoma/kwery/core/builder/QueryBuilder.kt b/core/src/main/kotlin/com/github/andrewoma/kwery/core/builder/QueryBuilder.kt
index f95a031..f13e51c 100644
--- a/core/src/main/kotlin/com/github/andrewoma/kwery/core/builder/QueryBuilder.kt
+++ b/core/src/main/kotlin/com/github/andrewoma/kwery/core/builder/QueryBuilder.kt
@@ -41,13 +41,14 @@ class QueryBuilder {
     private var groupBy: String? = null
     private var having: String? = null
     private var orderBy: String? = null
+    private val joins: JoinGroup = JoinGroup()
 
     fun select(table: String) {
         selects.add(table)
     }
 
     fun parameter(name: String, value: Any?) {
-        params.put(name, value)
+        params[name] = value
     }
 
     fun groupBy(groupBy: String) {
@@ -62,13 +63,27 @@ class QueryBuilder {
         this.orderBy = orderBy
     }
 
-    fun whereGroup(operator: String = "and", block: FilterBuilder.() -> Unit) {
-        require(filters.countLeaves() == 0) { "There must be only one root filters group" }
-        filters = Filter.Group(operator)
-        block(FilterBuilder(filters))
+    fun whereGroup(operator: String = "and", block: FilterBuilder.() -> Unit): Unit = when (filters.countLeaves()) {
+        0 -> {
+            filters = Filter.Group(operator)
+            block(FilterBuilder(filters))
+        }
+        2 -> {
+            val wrapper = Filter.Group("and")
+            wrapper.filters.add(this@QueryBuilder.filters)
+            block(FilterBuilder(wrapper))
+            filters = wrapper
+        }
+        else -> {
+            val group = Filter.Group(operator)
+            block(FilterBuilder(group))
+            filters.filters.add(group)
+            Unit
+        }
     }
 
     inner class FilterBuilder(private val group: Filter.Group) {
+        val parameter = this@QueryBuilder::parameter
 
         fun where(where: String) {
             group.filters.add(Filter.Where(where))
@@ -81,10 +96,15 @@ class QueryBuilder {
         }
     }
 
+    fun joinGroup(block: JoinGroup.() -> Unit) {
+        joins.addBuilder(block)
+    }
+
     fun build(sb: StringBuilder = StringBuilder(), block: QueryBuilder.() -> Unit): Query {
         block(this)
 
         selects.joinTo(sb, "\n")
+        if (joins.builders.isNotEmpty()) { sb.append("\n").append(joins.build()) }
         if (filters.countLeaves() != 0) {
             sb.append("\nwhere ")
             appendConditions(sb, filters, true)
diff --git a/core/src/test/kotlin/com/github/andrewoma/kwery/core/builder/AdvancedTests.kt b/core/src/test/kotlin/com/github/andrewoma/kwery/core/builder/AdvancedTests.kt
new file mode 100644
index 0000000..50bb063
--- /dev/null
+++ b/core/src/test/kotlin/com/github/andrewoma/kwery/core/builder/AdvancedTests.kt
@@ -0,0 +1,166 @@
+package com.github.andrewoma.kwery.core.builder
+
+import org.amshove.kluent.`should be equal to`
+import org.amshove.kluent.`should equal`
+import org.junit.Test
+
+class AdvancedTests {
+
+    @Test fun `Multiple root where groups`() {
+        query {
+            select("SELECT * FROM PERSON p")
+            whereGroup {
+                where("p.PERS_ID = '25'")
+            }
+            whereGroup {
+                where("p.SITE_ID = '100'")
+            }
+            whereGroup {
+                where("p.MERGE = '500'")
+            }
+        }.sql.trimQuery() `should be equal to` """
+            SELECT * FROM PERSON p
+            where
+            (p.PERS_ID = '25' and p.SITE_ID = '100') and p.MERGE = '500'
+        """.trimQuery()
+    }
+
+    @Test fun `Single root where group`() {
+        query {
+            select("SELECT * FROM PERSON p")
+            whereGroup {
+                where("p.PERS_ID = '25'")
+            }
+        }.sql.trimQuery() `should be equal to` """
+            SELECT * FROM PERSON p
+            where p.PERS_ID = '25'
+        """.trimQuery()
+    }
+
+    @Test fun `Two root where groups`() {
+        query {
+            select("SELECT * FROM PERSON p")
+            whereGroup {
+                where("p.PERS_ID = '25'")
+            }
+            whereGroup {
+                where("p.SITE_ID = '500'")
+            }
+        }.sql.trimQuery() `should be equal to` """
+            SELECT * FROM PERSON p
+            where p.PERS_ID = '25' and p.SITE_ID = '500'
+        """.trimQuery()
+    }
+
+    @Test fun `Nested and multi where groups`() {
+        query {
+            select("SELECT * FROM PERSON p")
+            whereGroup {
+                where("p.PERS_ID = '25'")
+            }
+            whereGroup {
+                whereGroup {
+                    where("p.SITE_ID = '500'")
+                    where("p.SITE_ID = '500'")
+                    where("p.SITE_ID = '500'")
+                }
+            }
+        }.sql.trimQuery() `should be equal to` """
+            SELECT * FROM PERSON p
+            where p.PERS_ID = '25' and
+            (p.SITE_ID = '500' and p.SITE_ID = '500' and p.SITE_ID = '500')
+        """.trimQuery()
+    }
+
+    @Test fun `Multiple join groups`() {
+        query {
+            select("SELECT * FROM PERSON p")
+            joinGroup {
+                innerJoin("SITE_PERS", "sp") { "$it.PERS_ID = p.PERS_ID" }
+            }
+            joinGroup {
+                innerJoin("SITE_PERS2", "sp2") { "$it.PERS_ID = p.PERS_ID" }
+            }
+        }.sql.trimQuery() `should be equal to` """
+            SELECT * FROM PERSON p
+            inner join SITE_PERS sp on sp.PERS_ID = p.PERS_ID
+            inner join SITE_PERS2 sp2 on sp2.PERS_ID = p.PERS_ID
+        """.trimQuery()
+    }
+
+    @Test fun `Multiple join and where groups`() {
+        query {
+            select("SELECT * FROM PERSON p")
+            whereGroup {
+                where("p.PERS_ID = '25'")
+            }
+            whereGroup {
+                where("p.SITE_ID = '100'")
+            }
+            joinGroup {
+                innerJoin("SITE_PERS", "sp") { "$it.PERS_ID = p.PERS_ID" }
+                innerJoin("SITE_PERS", "sp2") { "$it.PERS_ID = p.PERS_ID" }
+            }
+            joinGroup {
+                leftJoin("SOMETHING") { "$it.APB_ID = sp.Q_ID" }
+            }
+        }.sql.trimQuery() `should be equal to` """
+            SELECT * FROM PERSON p
+            inner join SITE_PERS sp on sp.PERS_ID = p.PERS_ID
+            inner join SITE_PERS sp2 on sp2.PERS_ID = p.PERS_ID
+            left join SOMETHING s on s.APB_ID = sp.Q_ID
+            where p.PERS_ID = '25' and p.SITE_ID = '100'
+        """.trimQuery()
+    }
+
+    @Test fun `Creating an where extension`() {
+        fun QueryBuilder.FilterBuilder.where() {
+            where("a = :b")
+            parameter(":b", "abc")
+        }
+        query {
+            whereGroup {
+                where()
+            }
+        }.parameters `should equal` mapOf(":b" to "abc")
+    }
+
+
+    @Test fun `Simple union sample`() {
+        (query {
+            select("SELECT * FROM SITE")
+        } union query {
+            select("SELECT * FROM PERSON")
+        }).sql `should be equal to` "SELECT * FROM SITE UNION SELECT * FROM PERSON"
+    }
+
+    @Test fun `Unions with parameters`() {
+        val result = query {
+            select("SELECT p.ID AS ID, p.NAME FROM dbo.PERSON p")
+            whereGroup {
+                where("p.ID = :id")
+                parameter("id", 25)
+            }
+        } unionAll query {
+            select("SELECT dp.PERS_ID as ID, dp.PERS_NAME as NAME FROM dbi.PERSON dp")
+            joinGroup {
+                leftJoin("SITE_PERS", "sp") { "$it.SITE_ID = dp.SITE_ID" }
+            }
+            whereGroup {
+                where("p.ID = :dpid")
+                parameter("dpid", 25)
+            }
+        }
+
+        result.sql `should be equal to` """
+            SELECT p.ID AS ID, p.NAME FROM dbo.PERSON p
+            where p.ID = :id UNION ALL SELECT dp.PERS_ID as ID, dp.PERS_NAME as NAME FROM dbi.PERSON dp
+            left join SITE_PERS sp on sp.SITE_ID = dp.SITE_ID
+            where p.ID = :dpid
+        """.trimIndent()
+
+        result.parameters["id"] `should equal` 25
+        result.parameters["dpid"] `should equal` 25
+        result.parameters.size `should be equal to` 2
+    }
+}
diff --git a/core/src/test/kotlin/com/github/andrewoma/kwery/core/builder/TestUtil.kt b/core/src/test/kotlin/com/github/andrewoma/kwery/core/builder/TestUtil.kt
new file mode 100644
index 0000000..051c901
--- /dev/null
+++ b/core/src/test/kotlin/com/github/andrewoma/kwery/core/builder/TestUtil.kt
@@ -0,0 +1,6 @@
+package com.github.andrewoma.kwery.core.builder
+
+fun String.trimQuery() = this
+    .trimIndent()
+    .split("\n")
+    .fold("") { acc, r -> "$acc\n${r.trim()}" }