sql, column switch line

 

Reference Links: https://blog.csdn.net/rainyspring4540/article/details/50231435

 

t_vehicle table has the following data:

　　

 

 sql initialization statement is as follows:

-- ----------------------------
-- Table structure for t_vehicle
-- ----------------------------
DROP TABLE IF EXISTS `t_vehicle`;
CREATE TABLE `t_vehicle` (
  `Vehicle_no` varchar(20) DEFAULT NULL,
  `Type` varchar(20) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

-- ----------------------------
-- Records of t_vehicle
-- ----------------------------
INSERT INTO `t_vehicle` VALUES ('粤B11', 'A');
INSERT INTO `t_vehicle` VALUES ('粤B11', 'B');
INSERT INTO `t_vehicle` VALUES ('粤B11', 'B');
INSERT INTO `t_vehicle` VALUES ('粤B22', 'C');

View Code

 

Now to achieve a query and returns the results as follows:

　　

 

Here involves grouping query, the query result and the line switching operation in a column, the sql written as follows:

select
    t.Vehicle_no,
    max(CASE t.Type WHEN 'A' THEN t.ct ELSE 0 END ) A_count,
    max(CASE t.Type WHEN 'B' THEN t.ct ELSE 0 END ) B_count,
    max(CASE t.Type WHEN 'C' THEN t.ct ELSE 0 END ) C_count
from (select Vehicle_no, Type, count(1) ct from t_vehicle group by Vehicle_no, Type)t
group by t.Vehicle_no

Note that only considered here to realize the function, without considering the sql query performance.