### Database Schema
CREATE TABLE `Third_Party_Companies` (
`company_id` INTEGER PRIMARY KEY ,
`company_type` VARCHAR(5) NOT NULL,
`company_name` VARCHAR(255),
`company_address` VARCHAR(255),
`other_company_details` VARCHAR(255)
)

CREATE TABLE `Maintenance_Contracts` (
`maintenance_contract_id` INTEGER PRIMARY KEY,
`maintenance_contract_company_id` INTEGER NOT NULL,
`contract_start_date` DATETIME,
`contract_end_date` DATETIME,
`other_contract_details` VARCHAR(255),
FOREIGN KEY (`maintenance_contract_company_id` ) REFERENCES `Third_Party_Companies`(`company_id` )
)

CREATE TABLE `Parts` (
`part_id` INTEGER PRIMARY KEY,
`part_name` VARCHAR(255),
`chargeable_yn` VARCHAR(1),
`chargeable_amount` VARCHAR(20),
`other_part_details` VARCHAR(255)
)

CREATE TABLE `Skills` (
`skill_id` INTEGER PRIMARY KEY,
`skill_code` VARCHAR(20),
`skill_description` VARCHAR(255)
)

CREATE TABLE `Staff` (
`staff_id` INTEGER PRIMARY KEY,
`staff_name` VARCHAR(255),
`gender` VARCHAR(1),
`other_staff_details` VARCHAR(255)
)

CREATE TABLE `Assets` (
`asset_id` INTEGER PRIMARY KEY,
`maintenance_contract_id` INTEGER NOT NULL,
`supplier_company_id` INTEGER NOT NULL,
`asset_details` VARCHAR(255),
`asset_make` VARCHAR(20),
`asset_model` VARCHAR(20),
`asset_acquired_date` DATETIME,
`asset_disposed_date` DATETIME,
`other_asset_details` VARCHAR(255),
FOREIGN KEY (`maintenance_contract_id` )
REFERENCES `Maintenance_Contracts`(`maintenance_contract_id` ),
FOREIGN KEY (`supplier_company_id` ) REFERENCES `Third_Party_Companies`(`company_id` )
)

CREATE TABLE `Asset_Parts` (
`asset_id` INTEGER NOT NULL,
`part_id` INTEGER NOT NULL,
FOREIGN KEY (`part_id` ) REFERENCES `Parts`(`part_id` ),
FOREIGN KEY (`asset_id` ) REFERENCES `Assets`(`asset_id` )
)

CREATE TABLE `Maintenance_Engineers` (
`engineer_id` INTEGER PRIMARY KEY,
`company_id` INTEGER NOT NULL,
`first_name` VARCHAR(50),
`last_name` VARCHAR(50),
`other_details` VARCHAR(255),
FOREIGN KEY (`company_id` ) REFERENCES `Third_Party_Companies`(`company_id` )
)

CREATE TABLE `Engineer_Skills` (
`engineer_id` INTEGER NOT NULL,
`skill_id` INTEGER NOT NULL,
FOREIGN KEY (`engineer_id` ) REFERENCES `Maintenance_Engineers`(`engineer_id` ),
FOREIGN KEY (`skill_id` ) REFERENCES `Skills`(`skill_id` )
)

CREATE TABLE `Fault_Log` (
`fault_log_entry_id` INTEGER PRIMARY KEY,
`asset_id` INTEGER NOT NULL,
`recorded_by_staff_id` INTEGER NOT NULL,
`fault_log_entry_datetime` DATETIME,
`fault_description` VARCHAR(255),
`other_fault_details` VARCHAR(255),
FOREIGN KEY (`asset_id` ) REFERENCES `Assets`(`asset_id` ),
FOREIGN KEY (`recorded_by_staff_id` ) REFERENCES `Staff`(`staff_id` )
)

CREATE TABLE `Engineer_Visits` (
`engineer_visit_id` INTEGER PRIMARY KEY,
`contact_staff_id` INTEGER,
`engineer_id` INTEGER NOT NULL,
`fault_log_entry_id` INTEGER NOT NULL,
`fault_status` VARCHAR(10) NOT NULL,
`visit_start_datetime` DATETIME,
`visit_end_datetime` DATETIME,
`other_visit_details` VARCHAR(255),
FOREIGN KEY (`fault_log_entry_id` ) REFERENCES `Fault_Log`(`fault_log_entry_id` ),
FOREIGN KEY (`engineer_id` ) REFERENCES `Maintenance_Engineers`(`engineer_id` ),
FOREIGN KEY (`contact_staff_id` ) REFERENCES `Staff`(`staff_id` )
)

CREATE TABLE `Part_Faults` (
`part_fault_id` INTEGER PRIMARY KEY,
`part_id` INTEGER NOT NULL,
`fault_short_name` VARCHAR(20),
`fault_description` VARCHAR(255),
`other_fault_details` VARCHAR(255),
FOREIGN KEY (`part_id` ) REFERENCES `Parts`(`part_id` )
)

CREATE TABLE `Fault_Log_Parts` (
`fault_log_entry_id` INTEGER NOT NULL,
`part_fault_id` INTEGER NOT NULL,
`fault_status` VARCHAR(10) NOT NULL,
FOREIGN KEY (`part_fault_id` ) REFERENCES `Part_Faults`(`part_fault_id` ),
FOREIGN KEY (`fault_log_entry_id` ) REFERENCES `Fault_Log`(`fault_log_entry_id` )
)

CREATE TABLE `Skills_Required_To_Fix` (
`part_fault_id` INTEGER NOT NULL,
`skill_id` INTEGER NOT NULL,
FOREIGN KEY (`part_fault_id` ) REFERENCES `Part_Faults`(`part_fault_id` ),
FOREIGN KEY (`skill_id` ) REFERENCES `Skills`(`skill_id` )
)

### Question
Which skill is used in fixing the most number of faults? List the skill id and description.

### SQL
SELECT T1.skill_id ,  T1.skill_description FROM Skills AS T1 JOIN Skills_Required_To_Fix AS T2 ON T1.skill_id  =  T2.skill_id GROUP BY T1.skill_id ORDER BY count(*) DESC LIMIT 1