SQL例子

数据库左连接查询SQL例子：

SELECT
  shaya_bs_water_meter.id,
  shaya_bs_water_meter.`name`
FROM
  shaya_bs_water_meter
LEFT JOIN (
  SELECT DISTINCT
    shaya_bs_automatic_record.water_meter_id
  FROM
    shaya_bs_automatic_record
) b ON shaya_bs_water_meter.id = b.water_meter_id
WHERE
  shaya_bs_water_meter.if_automatic = 'automatic'

数据库分组统计

select name,sum(number) from zn_safe_manager_fire_equipment GROUP BY name;