示例：
SELECT
town_name,
count( 1 ) AS tj_num
FROM
jy_industrial
WHERE
1 = 1
GROUP BY
town_name
ORDER BY
tj_num DESC
查询行数，查了下，没有具体说清楚的
示例：
SELECT
town_name,
count( 1 ) AS tj_num
FROM
jy_industrial
WHERE
1 = 1
GROUP BY
town_name
ORDER BY
tj_num DESC
查询行数，查了下，没有具体说清楚的
