package liquibase.sqlgenerator.core;

 import liquibase.database.Database;

 import liquibase.database.core.DB2Database;

 import liquibase.database.core.FirebirdDatabase;

 import liquibase.database.core.InformixDatabase;

 import liquibase.database.core.SybaseASADatabase;

 import liquibase.database.core.SybaseDatabase;

 import liquibase.exception.ValidationErrors;

 import liquibase.sql.Sql;

 import liquibase.sql.UnparsedSql;

 import liquibase.sqlgenerator.SqlGeneratorChain;

 import liquibase.statement.core.DropColumnStatement;

 public class DropColumnGenerator extends AbstractSqlGenerator<DropColumnStatement> {

     @Override

     public ValidationErrors validate(DropColumnStatement dropColumnStatement, Database database,

             SqlGeneratorChain sqlGeneratorChain) {

         ValidationErrors validationErrors = new ValidationErrors();

         validationErrors.checkRequiredField("tableName", dropColumnStatement.getTableName());

         validationErrors.checkRequiredField("columnName", dropColumnStatement.getColumnName());

         return validationErrors;

     }

     @Override

     public Sql[] generateSql(DropColumnStatement statement, Database database, SqlGeneratorChain sqlGeneratorChain) {

         if (database instanceof DB2Database) {

             return new Sql[] { new UnparsedSql("ALTER TABLE "

                     + database.escapeTableName(statement.getSchemaName(), statement.getTableName())

                     + " DROP COLUMN "

                     + database.escapeColumnName(statement.getSchemaName(), statement.getTableName(),

                             statement.getColumnName())) };

         } else if (database instanceof SybaseDatabase || database instanceof SybaseASADatabase

                 || database instanceof FirebirdDatabase || database instanceof InformixDatabase) {

             return new Sql[] { new UnparsedSql("ALTER TABLE "

                     + database.escapeTableName(statement.getSchemaName(), statement.getTableName())

                     + " DROP "

                     + database.escapeColumnName(statement.getSchemaName(), statement.getTableName(),

                             statement.getColumnName())) };

         }

         return new Sql[] { new UnparsedSql("ALTER TABLE "

                 + database.escapeTableName(statement.getSchemaName(), statement.getTableName())

                 + " DROP COLUMN "

                 + database.escapeColumnName(statement.getSchemaName(), statement.getTableName(),

                         statement.getColumnName())) };

     }

 }