#94 Added CAST function support

doc/changes/changelog.md

@@ -1,5 +1,6 @@
 # Changes
 
+* [4.3.0](changes_4.3.0.md)
 * [4.2.0](changes_4.2.0.md)
 * [4.1.0](changes_4.1.0.md)
 * [4.0.0](changes_4.0.0.md)

doc/changes/changes_4.3.0.md

@@ -0,0 +1,7 @@
+# SQL Statement Builder 4.3.0, released 2020-XX-XX
+
+Code Name: CAST function support
+
+## Features / Enhancements
+
+* #94: Added CAST function support

pom.xml

@@ -4,7 +4,7 @@
     <modelVersion>4.0.0</modelVersion>
     <groupId>com.exasol</groupId>
     <artifactId>sql-statement-builder</artifactId>
-    <version>4.2.0</version>
+    <version>4.3.0</version>
     <name>Exasol SQL Statement Builder</name>
     <description>This module provides a Builder for SQL statements that helps creating the correct structure and
         validates variable parts of the statements.

src/main/java/com/exasol/sql/dql/select/Select.java

@@ -3,10 +3,15 @@
 import java.util.ArrayList;
 import java.util.List;
 
-import com.exasol.sql.*;
+import com.exasol.datatype.type.DataType;
+import com.exasol.sql.AbstractFragment;
+import com.exasol.sql.ColumnsDefinition;
+import com.exasol.sql.DerivedColumn;
+import com.exasol.sql.SqlStatement;
 import com.exasol.sql.expression.*;
 import com.exasol.sql.expression.function.Function;
 import com.exasol.sql.expression.function.FunctionName;
+import com.exasol.sql.expression.function.exasol.ExasolCastFunction;
 
 /**
  * This class implements an SQL {@link Select} statement.
@@ -79,6 +84,32 @@ public Select function(final FunctionName functionName, final String derivedColu
         return this;
     }
 
+    /**
+     * Add a cast function.
+     *
+     * @param value value to cast
+     * @param type  type to cast the value to
+     * @return <code>this</code> instance for fluent programming
+     */
+    public Select cast(final ValueExpression value, final DataType type) {
+        return this.cast(value, type, "");
+    }
+
+    /**
+     * Add a cast function.
+     * 
+     * @param value             value to cast
+     * @param type              type to cast the value to
+     * @param derivedColumnName name under which you can refer to the derived column
+     * @return <code>this</code> instance for fluent programming
+     */
+    public Select cast(final ValueExpression value, final DataType type, final String derivedColumnName) {
+        final Function castFunction = ExasolCastFunction.of(value, type);
+        final DerivedColumn derivedColumn = new DerivedColumn(this, castFunction, derivedColumnName);
+        this.derivedColumns.add(derivedColumn);
+        return this;
+    }
+
     /**
      * Add a User Defined Function.
      *

src/main/java/com/exasol/sql/expression/ValueExpressionVisitor.java

@@ -1,6 +1,7 @@
 package com.exasol.sql.expression;
 
 import com.exasol.sql.UnnamedPlaceholder;
+import com.exasol.sql.expression.function.exasol.ExasolCastFunction;
 import com.exasol.sql.expression.function.exasol.ExasolFunction;
 import com.exasol.sql.expression.function.exasol.ExasolUdf;
 
@@ -41,4 +42,6 @@ public interface ValueExpressionVisitor {
     public void visit(NullLiteral nullLiteral);
 
     public void visit(BooleanExpression booleanExpression);
+
+    public void visit(ExasolCastFunction castFunction);
 }

src/main/java/com/exasol/sql/expression/function/exasol/ExasolCastFunction.java

@@ -0,0 +1,60 @@
+package com.exasol.sql.expression.function.exasol;
+
+import java.util.List;
+
+import com.exasol.datatype.type.DataType;
+import com.exasol.sql.expression.ValueExpression;
+import com.exasol.sql.expression.ValueExpressionVisitor;
+import com.exasol.sql.expression.function.AbstractFunction;
+
+/**
+ * This class represents the Exasol CAST function.
+ */
+public class ExasolCastFunction extends AbstractFunction {
+    private static final String CAST_FUNCTION_NAME = "CAST";
+    private final DataType type;
+
+    private ExasolCastFunction(final ValueExpression value, final DataType type) {
+        super(CAST_FUNCTION_NAME, List.of(value));
+        this.type = type;
+    }
+
+    /**
+     * Create a new {@link ExasolCastFunction} instance.
+     *
+     * @param valueExpression value to cast
+     * @param type            type to cast the value to
+     * @return new {@link ExasolCastFunction}
+     */
+    public static ExasolCastFunction of(final ValueExpression valueExpression, final DataType type) {
+        return new ExasolCastFunction(valueExpression, type);
+    }
+
+    /**
+     * Get the value to cast.
+     * 
+     * @return value to cast
+     */
+    public ValueExpression getValue() {
+        return this.valueExpressions.get(0);
+    }
+
+    /**
+     * Get the type to cast the value to.
+     * 
+     * @return type to cast the value to
+     */
+    public DataType getType() {
+        return this.type;
+    }
+
+    @Override
+    public boolean hasParenthesis() {
+        return true;
+    }
+
+    @Override
+    public void accept(final ValueExpressionVisitor visitor) {
+        visitor.visit(this);
+    }
+}

src/main/java/com/exasol/sql/expression/rendering/ValueExpressionRenderer.java

@@ -4,6 +4,7 @@
 import com.exasol.sql.UnnamedPlaceholder;
 import com.exasol.sql.expression.*;
 import com.exasol.sql.expression.function.Function;
+import com.exasol.sql.expression.function.exasol.ExasolCastFunction;
 import com.exasol.sql.expression.function.exasol.ExasolFunction;
 import com.exasol.sql.expression.function.exasol.ExasolUdf;
 import com.exasol.sql.rendering.ColumnsDefinitionRenderer;
@@ -55,7 +56,7 @@ public void visit(final FloatLiteral literal) {
     }
 
     @Override
-    public void visit(BigDecimalLiteral literal) {
+    public void visit(final BigDecimalLiteral literal) {
         appendCommaWhenNeeded(literal);
         append(literal.toString());
         setLastVisited(literal);
@@ -165,4 +166,16 @@ public void visit(final BooleanExpression booleanExpression) {
         booleanExpression.accept(expressionRenderer);
         append(expressionRenderer.render());
     }
+
+    @Override
+    public void visit(final ExasolCastFunction castFunction) {
+        appendKeyword("CAST");
+        startParenthesis();
+        castFunction.getValue().accept(this);
+        appendKeyword(" AS");
+        final ColumnsDefinitionRenderer columnsDefinitionRenderer = new ColumnsDefinitionRenderer(this.config);
+        castFunction.getType().accept(columnsDefinitionRenderer);
+        append(columnsDefinitionRenderer.render());
+        endParenthesis();
+    }
 }

src/test/java/com/exasol/sql/expression/function/exasol/ExasolCastFunctionTest.java

@@ -0,0 +1,27 @@
+package com.exasol.sql.expression.function.exasol;
+
+import static com.exasol.hamcrest.SqlFragmentRenderResultMatcher.rendersTo;
+import static org.hamcrest.MatcherAssert.assertThat;
+
+import org.junit.jupiter.api.Test;
+
+import com.exasol.datatype.type.Varchar;
+import com.exasol.sql.StatementFactory;
+import com.exasol.sql.dql.select.Select;
+import com.exasol.sql.expression.NullLiteral;
+
+class ExasolCastFunctionTest {
+
+    @Test
+    void testRendering() {
+        final Select select = StatementFactory.getInstance().select().cast(NullLiteral.nullLiteral(), new Varchar(254));
+        assertThat(select, rendersTo("SELECT CAST(NULL AS VARCHAR(254))"));
+    }
+
+    @Test
+    void testRenderingWithName() {
+        final Select select = StatementFactory.getInstance().select().cast(NullLiteral.nullLiteral(), new Varchar(254),
+                "TEST");
+        assertThat(select, rendersTo("SELECT CAST(NULL AS VARCHAR(254)) TEST"));
+    }
+}