SQL optimization for GROUP by statements

SQL statement:

Select T.type, COUNT (t.id) as Todo_count from Mc_job_form t where t.state = ' 2 ' and T.customs_code =: a GROUP by T.type

Table structure:

ID VARCHAR2 (N) ID

In_out_flag CHAR (1) Y

PROVIDER_ID number Y

apply_form_id VARCHAR2 (Y)

declare_apply_id VARCHAR2 (Y)

proposer_id VARCHAR2 (Y)

manual_id CHAR (Y)

Trade_type VARCHAR2 (3) Y

Company_code CHAR (Y)

Company_Name NVARCHAR2 (m) Y

Provider_name NVARCHAR2 (m) Y

Gross_weight number (19,5) Y

Net_weight number (19,5) Y

AMOUNT number (19,5) Y

Wrap_type VARCHAR2 (Y)

Trunk_no NVARCHAR2 (255) Y

Create_time DATE Y

Declare_time DATE Y

In_time DATE Y

Customs_code CHAR (4) Y

PORT CHAR (4) Y

Remark NVARCHAR2 (255) Y

State CHAR (1) Y

COMMENTS NVARCHAR2 (Y)

TYPE VARCHAR2 (2) Y

Proposer NVARCHAR2 (Y)

Out_time DATE Y

Proposer_phone VARCHAR2 (Y)

Contract_no VARCHAR2 (Y)

Tally_comments NVARCHAR2 (Y)

Tally_time DATE Y

Tally_approve_comments NVARCHAR2 (Y)

asso_job_form_id VARCHAR2 (Y)

Data_origin CHAR (1) Y

Guaranty_amount number (19,5) Y

Asso_flag CHAR (1) Y

Area_type CHAR (1) Y