Add Support for Sub-Queries in Select Statement "from" Clauses

CHANGELOG.md

@@ -35,6 +35,8 @@ Kotlin DSL.
 
 - Added a new sort specification that is useful in selects with joins ([#269](https://github.com/mybatis/mybatis-dynamic-sql/pull/269))
 - Added the capability to generate a camel cased alias for a column ([#272](https://github.com/mybatis/mybatis-dynamic-sql/issues/272))
+- Added sub-query support for "from" clauses in a select statement ([#282](https://github.com/mybatis/mybatis-dynamic-sql/pull/282))
+- Added Kotlin DSL updates to support sub-queries in select statements, where clauses, and insert statements ([#282](https://github.com/mybatis/mybatis-dynamic-sql/pull/282))
 
 ## Release 1.2.1 - September 29, 2020
 

src/main/java/org/mybatis/dynamic/sql/DerivedColumn.java

@@ -0,0 +1,129 @@
+/*
+ *    Copyright 2016-2020 the original author or authors.
+ *
+ *    Licensed under the Apache License, Version 2.0 (the "License");
+ *    you may not use this file except in compliance with the License.
+ *    You may obtain a copy of the License at
+ *
+ *       http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *    Unless required by applicable law or agreed to in writing, software
+ *    distributed under the License is distributed on an "AS IS" BASIS,
+ *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *    See the License for the specific language governing permissions and
+ *    limitations under the License.
+ */
+package org.mybatis.dynamic.sql;
+
+import java.sql.JDBCType;
+import java.util.Objects;
+import java.util.Optional;
+
+import org.mybatis.dynamic.sql.render.TableAliasCalculator;
+
+/**
+ * A derived column is a column that is not directly related to a table. This is primarily
+ * used for supporting sub-queries. The main difference in this class and {@link SqlColumn} is
+ * that this class does not have a related {@link SqlTable} and therefore ignores any table
+ * qualifier set in a query. If a table qualifier is required it can be set directly in the
+ * builder for this class.
+ *
+ * @param <T> The Java type that corresponds to this column - not used except for compiler type checking
+ *           for conditions
+ */
+public class DerivedColumn<T> implements BindableColumn<T> {
+    private final String name;
+    private final String tableQualifier;
+    private final String columnAlias;
+    private final JDBCType jdbcType;
+    private final String typeHandler;
+
+    protected DerivedColumn(Builder<T> builder) {
+        this.name = Objects.requireNonNull(builder.name);
+        this.tableQualifier = builder.tableQualifier;
+        this.columnAlias = builder.columnAlias;
+        this.jdbcType = builder.jdbcType;
+        this.typeHandler = builder.typeHandler;
+    }
+
+    @Override
+    public Optional<String> alias() {
+        return Optional.ofNullable(columnAlias);
+    }
+
+    @Override
+    public Optional<JDBCType> jdbcType() {
+        return Optional.ofNullable(jdbcType);
+    }
+
+    @Override
+    public Optional<String> typeHandler() {
+        return Optional.ofNullable(typeHandler);
+    }
+
+    @Override
+    public String renderWithTableAlias(TableAliasCalculator tableAliasCalculator) {
+        return tableQualifier == null ? name : tableQualifier + "." + name; //$NON-NLS-1$
+    }
+
+    @Override
+    public DerivedColumn<T> as(String columnAlias) {
+        return new Builder<T>()
+                .withName(name)
+                .withColumnAlias(columnAlias)
+                .withJdbcType(jdbcType)
+                .withTypeHandler(typeHandler)
+                .withTableQualifier(tableQualifier)
+                .build();
+    }
+
+    public static <T> DerivedColumn<T> of(String name) {
+        return new Builder<T>()
+                .withName(name)
+                .build();
+    }
+
+    public static <T> DerivedColumn<T> of(String name, String tableQualifier) {
+        return new Builder<T>()
+                .withName(name)
+                .withTableQualifier(tableQualifier)
+                .build();
+    }
+
+    public static class Builder<T> {
+        private String name;
+        private String tableQualifier;
+        private String columnAlias;
+        private JDBCType jdbcType;
+        private String typeHandler;
+
+        public Builder<T> withName(String name) {
+            this.name = name;
+            return this;
+        }
+
+        public Builder<T> withTableQualifier(String tableQualifier) {
+            this.tableQualifier = tableQualifier;
+            return this;
+        }
+
+        public Builder<T> withColumnAlias(String columnAlias) {
+            this.columnAlias = columnAlias;
+            return this;
+        }
+
+        public Builder<T> withJdbcType(JDBCType jdbcType) {
+            this.jdbcType = jdbcType;
+            return this;
+        }
+
+        public Builder<T> withTypeHandler(String typeHandler) {
+            this.typeHandler = typeHandler;
+            return this;
+        }
+
+        public DerivedColumn<T> build() {
+            return new DerivedColumn<>(this);
+        }
+    }
+}

src/main/java/org/mybatis/dynamic/sql/SqlBuilder.java

@@ -17,6 +17,7 @@
 
 import java.util.Arrays;
 import java.util.Collection;
+import java.util.List;
 import java.util.Objects;
 import java.util.function.Supplier;
 
@@ -760,6 +761,11 @@ public InsertSelectDSL.SelectGatherer withColumnList(SqlColumn<?>...columns) {
                     .withColumnList(columns);
         }
 
+        public InsertSelectDSL.SelectGatherer withColumnList(List<SqlColumn<?>> columns) {
+            return InsertSelectDSL.insertInto(table)
+                    .withColumnList(columns);
+        }
+
         public <T> GeneralInsertDSL.SetClauseFinisher<T> set(SqlColumn<T> column) {
             return GeneralInsertDSL.insertInto(table)
                     .set(column);

src/main/java/org/mybatis/dynamic/sql/SqlColumn.java

@@ -18,6 +18,7 @@
 import java.sql.JDBCType;
 import java.util.Objects;
 import java.util.Optional;
+import java.util.function.BiFunction;
 
 import org.jetbrains.annotations.NotNull;
 import org.mybatis.dynamic.sql.render.RenderingStrategy;
@@ -34,6 +35,7 @@ public class SqlColumn<T> implements BindableColumn<T>, SortSpecification {
     protected final String typeHandler;
     protected final RenderingStrategy renderingStrategy;
     protected final ParameterTypeConverter<T, ?> parameterTypeConverter;
+    protected final BiFunction<TableAliasCalculator, SqlTable, Optional<String>> tableQualifierFunction;
 
     private SqlColumn(Builder<T> builder) {
         name = Objects.requireNonNull(builder.name);
@@ -44,6 +46,7 @@ private SqlColumn(Builder<T> builder) {
         typeHandler = builder.typeHandler;
         renderingStrategy = builder.renderingStrategy;
         parameterTypeConverter = builder.parameterTypeConverter;
+        tableQualifierFunction = Objects.requireNonNull(builder.tableQualifierFunction);
     }
 
     public String name() {
@@ -86,6 +89,19 @@ public SqlColumn<T> as(String alias) {
         return b.withAlias(alias).build();
     }
 
+    /**
+     * Override the calculated table qualifier if there is one. This is useful for sub-queries
+     * where the calculated table qualifier may not be correct in all cases.
+     *
+     * @param tableQualifier the table qualifier to apply to the rendered column name
+     * @return a new column that will be rendered with the specified table qualifier
+     */
+    public SqlColumn<T> qualifiedWith(String tableQualifier) {
+        Builder<T> b = copy();
+        b.withTableQualifierFunction((tac, t) -> Optional.of(tableQualifier));
+        return b.build();
+    }
+
     /**
      * Set an alias with a camel cased string based on the column name. The can be useful for queries using
      * the {@link org.mybatis.dynamic.sql.util.mybatis3.CommonSelectMapper} where the columns are placed into
@@ -114,7 +130,7 @@ public String orderByName() {
 
     @Override
     public String renderWithTableAlias(TableAliasCalculator tableAliasCalculator) {
-        return tableAliasCalculator.aliasForColumn(table)
+        return tableQualifierFunction.apply(tableAliasCalculator, table)
                 .map(this::applyTableAlias)
                 .orElseGet(this::name);
     }
@@ -160,8 +176,9 @@ private <S> Builder<S> copy() {
                 .withDescending(this.isDescending)
                 .withAlias(this.alias)
                 .withTypeHandler(this.typeHandler)
-                .withRenderingStrategy((this.renderingStrategy))
-                .withParameterTypeConverter((ParameterTypeConverter<S, ?>) this.parameterTypeConverter);
+                .withRenderingStrategy(this.renderingStrategy)
+                .withParameterTypeConverter((ParameterTypeConverter<S, ?>) this.parameterTypeConverter)
+                .withTableQualifierFunction(this.tableQualifierFunction);
     }
 
     private String applyTableAlias(String tableAlias) {
@@ -190,6 +207,8 @@ public static class Builder<T> {
         protected String typeHandler;
         protected RenderingStrategy renderingStrategy;
         protected ParameterTypeConverter<T, ?> parameterTypeConverter;
+        protected BiFunction<TableAliasCalculator, SqlTable, Optional<String>> tableQualifierFunction =
+                TableAliasCalculator::aliasForColumn;
 
         public Builder<T> withName(String name) {
             this.name = name;
@@ -231,6 +250,12 @@ public Builder<T> withParameterTypeConverter(ParameterTypeConverter<T, ?> parame
             return this;
         }
 
+        private Builder<T> withTableQualifierFunction(
+                BiFunction<TableAliasCalculator, SqlTable, Optional<String>> tableQualifierFunction) {
+            this.tableQualifierFunction = tableQualifierFunction;
+            return this;
+        }
+
         public SqlColumn<T> build() {
             return new SqlColumn<>(this);
         }

src/main/java/org/mybatis/dynamic/sql/SqlTable.java

@@ -22,7 +22,7 @@
 
 import org.jetbrains.annotations.NotNull;
 
-public class SqlTable {
+public class SqlTable implements TableExpression {
 
     private final Supplier<String> nameSupplier;
 
@@ -103,6 +103,11 @@ public <T> SqlColumn<T> column(String name, JDBCType jdbcType, String typeHandle
         return column.withTypeHandler(typeHandler);
     }
 
+    @Override
+    public <R> R accept(TableExpressionVisitor<R> visitor) {
+        return visitor.visit(this);
+    }
+
     public static SqlTable of(String name) {
         return new SqlTable(name);
     }

src/main/java/org/mybatis/dynamic/sql/TableExpression.java

@@ -0,0 +1,21 @@
+/*
+ *    Copyright 2016-2020 the original author or authors.
+ *
+ *    Licensed under the Apache License, Version 2.0 (the "License");
+ *    you may not use this file except in compliance with the License.
+ *    You may obtain a copy of the License at
+ *
+ *       http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *    Unless required by applicable law or agreed to in writing, software
+ *    distributed under the License is distributed on an "AS IS" BASIS,
+ *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *    See the License for the specific language governing permissions and
+ *    limitations under the License.
+ */
+package org.mybatis.dynamic.sql;
+
+public interface TableExpression {
+
+    <R> R accept(TableExpressionVisitor<R> visitor);
+}

src/main/java/org/mybatis/dynamic/sql/TableExpressionVisitor.java

@@ -0,0 +1,24 @@
+/*
+ *    Copyright 2016-2020 the original author or authors.
+ *
+ *    Licensed under the Apache License, Version 2.0 (the "License");
+ *    you may not use this file except in compliance with the License.
+ *    You may obtain a copy of the License at
+ *
+ *       http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *    Unless required by applicable law or agreed to in writing, software
+ *    distributed under the License is distributed on an "AS IS" BASIS,
+ *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *    See the License for the specific language governing permissions and
+ *    limitations under the License.
+ */
+package org.mybatis.dynamic.sql;
+
+import org.mybatis.dynamic.sql.select.SubQuery;
+
+public interface TableExpressionVisitor<R> {
+    R visit(SqlTable table);
+
+    R visit(SubQuery subQuery);
+}

src/main/java/org/mybatis/dynamic/sql/insert/InsertSelectDSL.java

@@ -61,7 +61,11 @@ private InsertColumnGatherer(SqlTable table) {
         }
 
         public SelectGatherer withColumnList(SqlColumn<?>...columns) {
-            return new SelectGatherer(table, Arrays.asList(columns));
+            return withColumnList(Arrays.asList(columns));
+        }
+
+        public SelectGatherer withColumnList(List<SqlColumn<?>> columns) {
+            return new SelectGatherer(table, columns);
         }
 
         public InsertSelectDSL withSelectStatement(Buildable<SelectModel> selectModelBuilder) {

src/main/java/org/mybatis/dynamic/sql/insert/InsertSelectModel.java

@@ -18,6 +18,7 @@
 import java.util.Objects;
 import java.util.Optional;
 
+import org.jetbrains.annotations.NotNull;
 import org.mybatis.dynamic.sql.SqlTable;
 import org.mybatis.dynamic.sql.insert.render.InsertSelectRenderer;
 import org.mybatis.dynamic.sql.insert.render.InsertSelectStatementProvider;
@@ -47,6 +48,7 @@ public Optional<InsertColumnListModel> columnList() {
         return Optional.ofNullable(columnList);
     }
 
+    @NotNull
     public InsertSelectStatementProvider render(RenderingStrategy renderingStrategy) {
         return InsertSelectRenderer.withInsertSelectModel(this)
                 .withRenderingStrategy(renderingStrategy)

src/main/java/org/mybatis/dynamic/sql/select/AbstractQueryExpressionDSL.java

@@ -25,6 +25,7 @@
 import java.util.stream.Collectors;
 
 import org.mybatis.dynamic.sql.SqlTable;
+import org.mybatis.dynamic.sql.TableExpression;
 import org.mybatis.dynamic.sql.select.join.JoinCriterion;
 import org.mybatis.dynamic.sql.select.join.JoinModel;
 import org.mybatis.dynamic.sql.select.join.JoinSpecification;
@@ -36,13 +37,13 @@ public abstract class AbstractQueryExpressionDSL<T extends AbstractQueryExpressi
 
     private final List<JoinSpecification.Builder> joinSpecificationBuilders = new ArrayList<>();
     protected final Map<SqlTable, String> tableAliases = new HashMap<>();
-    private final SqlTable table;
+    private final TableExpression table;
 
-    protected AbstractQueryExpressionDSL(SqlTable table) {
+    protected AbstractQueryExpressionDSL(TableExpression table) {
         this.table = Objects.requireNonNull(table);
     }
 
-    public SqlTable table() {
+    public TableExpression table() {
         return table;
     }