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Custom syntax elements

Applies to ✅ Open Source Edition   ✅ Express Edition   ✅ Professional Edition   ✅ Enterprise Edition

To support simple vendor specific SQL syntax extensions, jOOQ offers the plain SQL templating API. If a SQL clause is too complex to express with jOOQ or with this templating API, or you have a requirement to support different dialects, you can extend either one of the following types for use directly in a jOOQ query:

// Simplified API description:
public abstract class CustomField<T> implements Field<T> {}
public abstract class CustomCondition implements Condition {}
public abstract class CustomTable<R extends TableRecord<R>> implements Table<R> {}
public abstract class CustomRecord<R extends TableRecord<R>> implements TableRecord<R> {}

An example for implementing a custom table and its record.

Here's an example org.jooq.impl.CustomTable showing how to create a custom table with its field definitions, similar to what the code generator is doing.

public class BookTable extends CustomTable<BookRecord> {
    public static final BookTable BOOK = new BookTable();

    public final TableField<BookRecord, String> FIRST_NAME = createField(name("FIRST_NAME"), SQLDataType.VARCHAR);
    public final TableField<BookRecord, String> UNMATCHED  = createField(name("UNMATCHED"), SQLDataType.VARCHAR);
    public final TableField<BookRecord, String> LAST_NAME  = createField(name("LAST_NAME"), SQLDataType.VARCHAR);
    public final TableField<BookRecord, Short>  ID         = createField(name("ID"), SQLDataType.SMALLINT);
    public final TableField<BookRecord, String> TITLE      = createField(name("TITLE"), SQLDataType.VARCHAR);

    protected BookTable() {
        super(name("BOOK"));
    }

    @Override
    public Class<? extends BookRecord> getRecordType() {
        return BookRecord.class;
    }
}

public class BookRecord extends CustomRecord<BookRecord> {
    protected BookRecord() {
        super(BookTable.BOOK);
    }
}

An example for implementing custom multiplication.

Here's an example org.jooq.impl.CustomField showing how to create a field multiplying another field by 2

// Create an anonymous CustomField, initialised with BOOK.ID arguments
final Field<Integer> IDx2 = new CustomField<Integer>(BOOK.ID.getName(), BOOK.ID.getDataType()) {
    @Override
    public void accept(Context<?> context) {
        context.visit(BOOK.ID).sql(" * ").visit(DSL.val(2));
    }
};

// Use the above field in a SQL statement:
create.select(IDx2).from(BOOK);

An example for implementing vendor-specific functions.

Many vendor-specific functions are not officially supported by jOOQ, but you can implement such support yourself using CustomField, for instance. Here's an example showing how to implement Oracle's TO_CHAR() function, emulating it in SQL Server using CONVERT():

// Create a CustomField implementation taking two arguments in its constructor
class ToChar extends CustomField<String> {

    final Field<?> arg0;
    final Field<?> arg1;

    ToChar(Field<?> arg0, Field<?> arg1) {
        super("to_char", SQLDataType.VARCHAR);

        this.arg0 = arg0;
        this.arg1 = arg1;
    }

    @Override
    public void accept(RenderContext context) {
        context.visit(delegate(context.configuration()));
    }

    private QueryPart delegate(Configuration configuration) {
        switch (configuration.dialect().family()) {
            case ORACLE:
                return DSL.field("TO_CHAR({0}, {1})", String.class, arg0, arg1);

            case SQLSERVER:
                return DSL.field("CONVERT(VARCHAR(8), {0}, {1})", String.class, arg0, arg1);

            default:
                throw new UnsupportedOperationException("Dialect not supported");
        }
    }
}

The above CustomField implementation can be exposed from your own custom DSL class:

public class MyDSL {
    public static Field<String> toChar(Field<?> field, String format) {
        return new ToChar(field, DSL.inline(format));
    }
}
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