sql 語句，先降後分組

時間 2019-11-29

標籤 sql 語句分組欄目 SQL 简体版

原文原文鏈接

體溫表：sql

-- 體溫: Temperature
DROP TABLE IF EXISTS Temperature;
CREATE TABLE Temperature
(
ID_Card				VARCHAR(30) NOT NULL			COMMENT '身份證號',
Time			    DATETIME NOT NULL           	COMMENT '測量時間',
Temperature			FLOAT NOT NULL			        COMMENT '體溫',
Dtype               VARCHAR(100)                    COMMENT '設備類型',
Did                 VARCHAR(100)                    COMMENT '設備編碼',
Medic_Id            VARCHAR(100)                    COMMENT '醫生ID',
Note				TEXT		 					COMMENT '備註',
CONSTRAINT PK_Temperature PRIMARY KEY(ID_Card,Time)
);
ALTER TABLE Temperature COMMENT  = '體溫';

插入數據：函數

INSERT INTO temperature VALUES (11, '5329321990011', '2016-8-11 12:14:34', 11, NULL, NULL, NULL, NULL);
INSERT INTO temperature VALUES (13, '5329321990011', '2016-8-11 15:43:10', 21, NULL, NULL, NULL, NULL);
INSERT INTO temperature VALUES (14, '5329321990011', '2016-8-11 15:52:10', 11, NULL, NULL, NULL, NULL);
INSERT INTO temperature VALUES (15, '5329321990011', '2016-8-12 12:14:34', 2, NULL, NULL, NULL, NULL);
INSERT INTO temperature VALUES (16, '5329321990011', '2016-8-12 13:39:52', 333, NULL, NULL, NULL, NULL);
INSERT INTO temperature VALUES (17, '5329321990011', '2016-8-12 16:48:37', 1.2, NULL, NULL, NULL, NULL);
INSERT INTO temperature VALUES (21, '5329321990011', '2016-8-12 17:58:39', 42, NULL, NULL, NULL, NULL);
INSERT INTO temperature VALUES (24, '5329321990011', '2016-8-19 09:51:12', 100, NULL, NULL, NULL, NULL);
INSERT INTO temperature VALUES (24, '5329321990011', '2016-8-19 09:51:32', 101, NULL, NULL, NULL, NULL);
INSERT INTO temperature VALUES (24, '5329321990011', '2016-8-19 09:52:12', 103, NULL, NULL, NULL, NULL);
INSERT INTO temperature VALUES (24, '5329321990011', '2016-8-19 09:53:12', 107, NULL, NULL, NULL, NULL);
INSERT INTO temperature VALUES (25, '5301211998012', '2016-8-18 17:34:37', 55, NULL, NULL, NULL, NULL);
INSERT INTO temperature VALUES (26, '5329011995112', '2016-8-16 10:17:19', 12313, NULL, NULL, NULL, NULL);
INSERT INTO temperature VALUES (27, '5329011995112', '2016-8-18 11:47:24', 22, NULL, NULL, NULL, NULL);

需求：查詢出8月裏天天最新的一條數據一、第一步先降序：編碼

SELECT * FROM temperature ORDER BY Time DESC

二、第二步：排序後分組，GROUP BY time，用substr()函數截取時間後格式爲yyyyy-mm-dd，這樣就變成了按天進行分組，GROUP BY後默認顯示每組中的第一條數據。以下code

SELECT * FROM 
(SELECT * FROM temperature ORDER BY Time DESC) t1 WHERE t1.time>='2016-08-01 00:00:00' AND t1.time<'2016-09-01 00:00:00' GROUP BY substr(t1.time, 1, 10)

查詢查來的數據以下：排序