How to delete categories in Magento through database

The following queries will delete all categories in Magento:

TRUNCATE TABLE `catalog_category_entity`;
delete from catalog_category_entity where entity_id<3;
TRUNCATE TABLE `catalog_category_entity_datetime`;
TRUNCATE TABLE `catalog_category_entity_decimal`;
TRUNCATE TABLE `catalog_category_entity_int`;
TRUNCATE TABLE `catalog_category_entity_text`;
TRUNCATE TABLE `catalog_category_entity_varchar`;
TRUNCATE TABLE `catalog_category_product`;
TRUNCATE TABLE `catalog_category_product_index`;

After executed the above queries, you want to run the following queries to put back some default values:

insert  into `catalog_category_entity`(`entity_id`,`entity_type_id`,`attribute_set_id`,`parent_id`,`created_at`,`updated_at`,`path`,`position`,`level`,`children_count`) values (1,3,0,0,'0000-00-00 00:00:00','2009-02-20 00:25:34','1',1,0,1),(2,3,3,0,'2009-02-20 00:25:34','2009-02-20 00:25:34','1/2',1,1,0);
insert  into `catalog_category_entity_int`(`value_id`,`entity_type_id`,`attribute_id`,`store_id`,`entity_id`,`value`) values (1,3,32,0,2,1),(2,3,32,1,2,1);
insert  into `catalog_category_entity_varchar`(`value_id`,`entity_type_id`,`attribute_id`,`store_id`,`entity_id`,`value`) values (1,3,31,0,1,'Root Catalog'),(2,3,33,0,1,'root-catalog'),(3,3,31,0,2,'Default Category'),(4,3,39,0,2,'PRODUCTS'),(5,3,33,0,2,'default-category');

If the above queries give errors, that might be the version issues, then just go open the Magento sample data script you used to creat all the tables in Magento’s database, find and run the queries used to inserting data to those tables: catalog_category_entity, catalog_category_entity_int, and catalog_category_entity_varchar.