Aqui vem uma solução usando variáveis de usuário. Verifiquei com os dados que você forneceu e inseri mais dados para verificação.
Para salvar o resultado da consulta permanentemente e mantê-lo acessível posteriormente, o resultado é gravado em uma tabela tbl_new.
Demonstração completa>>
SQL:
-- data preparation
create table tbl(acct varchar(100), start_date date, end_date date);
insert into tbl values
('Acct-1', '2016-01-01', '2016-01-07'),
('Acct-1', '2016-01-05', '2016-01-11'),
('Acct-1', '2016-01-18', '2016-01-24'),
('Acct-1', '2016-02-02', '2016-02-08'),
('Acct-1', '2016-02-07', '2016-02-13'),
('Acct-2', '2016-01-01', '2016-01-07'),
('Acct-2', '2016-01-18', '2016-01-24'),
('Acct-2', '2016-01-02', '2016-02-08');
SELECT * FROM tbl;
-- Need queries
SET @last_acct = '', @last_start_date = '1970-01-01', @last_end_date = '9999-12-31', @group = 1;
CREATE TABLE tbl_new (acct varchar(100), start_date date, end_date date);
INSERT INTO tbl_new
SELECT
acct,
MIN(start_date) start_date,
MAX(end_date) end_date
FROM
(
SELECT
acct,
start_date,
end_date,
CASE
WHEN
acct = @last_acct AND start_date <= @last_end_date
THEN
@group
ELSE
@group := @group + 1
END group_num,
@last_acct := acct,
@last_start_date := start_date,
@last_end_date := end_date
FROM
tbl
) tbl2
GROUP BY group_num;
SELECT * FROM tbl_new;
Resultado:
mysql> SELECT * FROM tbl;
+--------+------------+------------+
| acct | start_date | end_date |
+--------+------------+------------+
| Acct-1 | 2016-01-01 | 2016-01-07 |
| Acct-1 | 2016-01-05 | 2016-01-11 |
| Acct-1 | 2016-01-18 | 2016-01-24 |
| Acct-1 | 2016-02-02 | 2016-02-08 |
| Acct-1 | 2016-02-07 | 2016-02-13 |
| Acct-2 | 2016-01-01 | 2016-01-07 |
| Acct-2 | 2016-01-18 | 2016-01-24 |
| Acct-2 | 2016-01-02 | 2016-02-08 |
+--------+------------+------------+
8 rows in set (0.00 sec)
mysql>
mysql> -- Need queries
mysql> SET @last_acct = '', @last_start_date = '1970-01-01', @last_end_date = '9999-12-31', @group = 1;
Query OK, 0 rows affected (0.00 sec)
mysql>
mysql> CREATE TABLE tbl_new (acct varchar(100), start_date date, end_date date);
Query OK, 0 rows affected (0.01 sec)
mysql>
mysql> INSERT INTO tbl_new
-> SELECT
-> acct,
-> MIN(start_date) start_date,
-> MAX(end_date) end_date
-> FROM
-> (
-> SELECT
-> acct,
-> start_date,
-> end_date,
-> CASE
-> WHEN
-> acct = @last_acct AND start_date <= @last_end_date
-> THEN
-> @group
-> ELSE
-> @group := @group + 1
-> END group_num,
-> @last_acct := acct,
-> @last_start_date := start_date,
-> @last_end_date := end_date
-> FROM
-> tbl
-> ) tbl2
-> GROUP BY group_num;
Query OK, 5 rows affected (0.00 sec)
Records: 5 Duplicates: 0 Warnings: 0
mysql>
mysql> SELECT * FROM tbl_new;
+--------+------------+------------+
| acct | start_date | end_date |
+--------+------------+------------+
| Acct-1 | 2016-01-01 | 2016-01-11 |
| Acct-1 | 2016-01-18 | 2016-01-24 |
| Acct-1 | 2016-02-02 | 2016-02-13 |
| Acct-2 | 2016-01-01 | 2016-01-07 |
| Acct-2 | 2016-01-02 | 2016-02-08 |
+--------+------------+------------+
5 rows in set (0.00 sec)
