Step 1 : Create a file name as service.xml in the WEB-INF folder
Step 2 : Write the following
service.xml
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE service-builder PUBLIC
"-//Liferay//DTD Service Builder 6.0.0//EN"
"http://www.liferay.com/dtd/liferay-service-builder_6_0_0.dtd">
<service-builder package-path="com.name.portlets.package"> <!-- as your require package structure you want -->
<namespace>servicebuilder</namespace> <!-- prefix of the table -->
<entity name="Table_Name" local-service="true" remote-service="false"> <!-- entry name is name of table -->

<column name="Column_One" type="long" primary="true" id-type="identity" /> <!--column fields in table-->
<column name="Column_Two" type="String"></column>
<column name="Column_Three" type="String"></column>

</entity>

</service-builder>
Step 3 : Start the Ant build service in build .xml of project

then it will create the tables in the database and as well as create the java code in project with respective package structure

It will create the tables only when the portlet or hook containing this service is deployed.

It will create a sql commands under the sql directory.