mysql行列變化,最難的就是將多個(gè)列變成多行,使用的比較多的是統(tǒng)計(jì)學(xué)中行變列,列變行,沒(méi)有找到現(xiàn)成的函數(shù)或者語(yǔ)句,所以自己寫(xiě)了存儲(chǔ)過(guò)程,使用動(dòng)態(tài)sql來(lái)實(shí)現(xiàn),應(yīng)用業(yè)務(wù)場(chǎng)景,用戶(hù)每個(gè)月都有使用記錄數(shù)錄入一張表,一個(gè)月一個(gè)字段,所以表的字段是動(dòng)態(tài)增長(zhǎng)的,現(xiàn)在需要實(shí)時(shí)統(tǒng)計(jì)當(dāng)前用戶(hù)使用的總數(shù)量,如果你知道有多少個(gè)字段,那么可以用select c1+c2+c3+…. From tbname where tid=’111’;來(lái)實(shí)現(xiàn),但是關(guān)鍵是這個(gè)都是動(dòng)態(tài)的,所以在應(yīng)用程序端來(lái)實(shí)現(xiàn)確實(shí)不適宜,可以放在數(shù)據(jù)庫(kù)后臺(tái)在存儲(chǔ)過(guò)程里實(shí)現(xiàn)。
而且在行變成列中,如果要寫(xiě)單個(gè)sql來(lái)實(shí)現(xiàn),列的數(shù)目就需要寫(xiě)死,因?yàn)槿绻恢酪故境啥嗌倭械脑?,就需要用?dòng)態(tài)變量,而一條sql里面無(wú)法使用動(dòng)態(tài)變量。但是可以使用sql塊來(lái)實(shí)現(xiàn)動(dòng)態(tài)的效果。
這是基礎(chǔ)數(shù)據(jù)表,里面有多個(gè)字段wm201403……,現(xiàn)在需要把N個(gè)這樣的列變成行數(shù)據(jù)。
USE csdn; DROP TABLE IF EXISTS flow_table; CREATE TABLE `flow_table` ( `ID` INT(11) NOT NULL AUTO_INCREMENT, `Number` BIGINT(11) NOT NULL, `City` VARCHAR(10) NOT NULL, `wm201403` DECIMAL(7,2) DEFAULT NULL, `wm201404` DECIMAL(7,2) DEFAULT NULL, `wm201405` DECIMAL(7,2) DEFAULT NULL, `wm201406` DECIMAL(7,2) DEFAULT NULL, `wm201407` DECIMAL(7,2) DEFAULT NULL, `wm201408` DECIMAL(7,2) DEFAULT NULL, PRIMARY KEY (`ID`,`Number`) ) ENGINE=INNODB DEFAULT CHARSET=utf8;
錄入一批測(cè)試數(shù)據(jù):
INSERT INTO flow_table(Number,City,wm201403,wm201404,wm201405,wm201406,wm201407,wm201408)SELECT 1,'shanghai',100.2,180.4,141,164,124,127; INSERT INTO flow_table(Number,City,wm201403,wm201404,wm201405,wm201406,wm201407,wm201408)SELECT 2,'shanghai',110.23,180.34,141.23,104.78,124.67,127.45; INSERT INTO flow_table(Number,City,wm201403,wm201404,wm201405,wm201406,wm201407,wm201408)SELECT 3,'beijing',123.23,110.34,131.33,154.58,154.67,167.45; INSERT INTO flow_table(Number,City,wm201403,wm201404,wm201405,wm201406,wm201407,wm201408)SELECT 4,'hangzhou',0,110.34,131.33,154.58,154.67,0; INSERT INTO flow_table(Number,City,wm201405,wm201406,wm201407,wm201408)SELECT 5,'hangzhou',131.33,154.58,154.67,0;
需要達(dá)到的統(tǒng)計(jì)效果是:
+--------+-----------+
| Number | total_num |
+--------+-----------+
| 1 | 836.60 |
| 2 | 788.70 |
| 3 | 841.60 |
| 4 | 550.92 |
| 5 | 440.58 |
+--------+-----------+
5 rows in set (0.00 sec)
這個(gè)存儲(chǔ)過(guò)程建立了2張臨時(shí)表,查詢(xún)測(cè)試表數(shù)據(jù)形成游標(biāo),遍歷游標(biāo)根據(jù)主鍵Number來(lái)調(diào)用pro_flow_modify存儲(chǔ)過(guò)程進(jìn)行行列變化。代碼如下:
DELIMITER $$ DROP PROCEDURE IF EXISTS csdn.`proc_all_changes`$$ CREATE PROCEDURE csdn.proc_all_changes() BEGIN DECLARE v_number BIGINT; DECLARE v_city VARCHAR(10); DECLARE _done INT DEFAULT 0; /*定義游標(biāo)*/ DECLARE cur_all CURSOR FOR SELECT Number,City FROM csdn.`flow_table`; /**這里如果需要定義下當(dāng)NOT FOUND的時(shí)候,EXIT退出游標(biāo)遍歷,不然如果設(shè)置成CONTINUE會(huì)一直執(zhí)行下去。*/ DECLARE EXIT HANDLER FOR NOT FOUND BEGIN SET _done=1;END; /*建立臨時(shí)表,存放所有字段的臨時(shí)表*/ DROP TABLE IF EXISTS flow_n_columns; CREATE TABLE `flow_n_columns` ( `column_name` VARCHAR(10) NOT NULL ) ENGINE=INNODB DEFAULT CHARSET=utf8; /*存放最終變成行的數(shù)據(jù)表*/ DROP TABLE IF EXISTS flow_tmp; CREATE TABLE `flow_tmp` ( `Number` INT(11) DEFAULT NULL, `City` VARCHAR(10) DEFAULT NULL, `wm_str` VARCHAR(10) DEFAULT NULL, `Wm` DECIMAL(7,2) DEFAULT NULL ) ENGINE=INNODB DEFAULT CHARSET=utf8; OPEN cur_all; REPEAT FETCH cur_all INTO v_number, v_city; IF NOT _done THEN CALL csdn.pro_flow_modify(v_number,v_city); END IF; UNTIL _done=1 END REPEAT; CLOSE cur_all; /*展示下所有的行轉(zhuǎn)列的數(shù)據(jù)**/ SELECT * FROM csdn.flow_tmp; END$$ DELIMITER ;
通過(guò)查詢(xún)系統(tǒng)表information_schema.`COLUMNS`來(lái)獲取測(cè)試表flow_table的所有列,然后寫(xiě)動(dòng)態(tài)SQL,來(lái)把列的值錄入到臨時(shí)表flow_tmp中。
DELIMITER $$ DROP PROCEDURE IF EXISTS csdn.`pro_flow_modify`$$ CREATE PROCEDURE csdn.`pro_flow_modify`(p_Number INT,p_city VARCHAR(10)) BEGIN DECLARE v_column_name VARCHAR(10) DEFAULT ''; DECLARE v_exe_sql VARCHAR(1000) DEFAULT ''; DECLARE v_start_wm VARCHAR(10) DEFAULT ''; DECLARE v_end_wm VARCHAR(10) DEFAULT ''; DECLARE v_num DECIMAL(10,2) DEFAULT 0; DECLARE i INT DEFAULT 1; DECLARE v_Number INT DEFAULT 0; SET v_Number=p_Number; DELETE FROM csdn.flow_n_columns; DELETE FROM csdn.flow_tmp WHERE Number=v_Number; /*把測(cè)試表flow_table的所有字段都錄入字段臨時(shí)表中,這樣就達(dá)到了從列變成行的目的*/ INSERT INTO flow_n_columns SELECT t.`COLUMN_NAME` FROM information_schema.`COLUMNS` t WHERE t.`TABLE_NAME`='flow_table' AND t.`TABLE_SCHEMA`='csdn' AND t.`COLUMN_NAME` NOT IN('ID','Number','City'); SELECT column_name INTO v_column_name FROM csdn.flow_n_columns LIMIT 1; /*開(kāi)始循環(huán)遍歷字段臨時(shí)表的字段數(shù)據(jù),并且把字段值放入臨時(shí)表flow_tmp里面*/ WHILE i>0 DO SET v_exe_sql=CONCAT('INSERT INTO csdn.flow_tmp(Number,City,wm_str,Wm) select ',v_Number,',\'',p_city, '\',\'',v_column_name,'\',',v_column_name,' from csdn.flow_table WHERE flow_table.Number=',v_Number,';'); SET @sql=v_exe_sql; PREPARE s1 FROM @sql; EXECUTE s1; DEALLOCATE PREPARE s1; DELETE FROM csdn.flow_n_columns WHERE column_name=v_column_name; SELECT column_name INTO v_column_name FROM csdn.flow_n_columns LIMIT 1; SELECT COUNT(1) INTO i FROM csdn.flow_n_columns ; DELETE FROM csdn.flow_tmp WHERE Wm=0; END WHILE; /*由于觸發(fā)器是不支持動(dòng)態(tài)sql,所以不能使用while循環(huán),動(dòng)態(tài)遍歷所有統(tǒng)計(jì)列的,只能寫(xiě)死列了,如下所示: 現(xiàn)在一個(gè)個(gè)insert只能寫(xiě)死了, flow_table表有多少個(gè)統(tǒng)計(jì)列就寫(xiě)多少個(gè)insert sql,以后新添加一個(gè)列,就在這里新添加一條insertsql語(yǔ)句 INSERT INTO flow_tmp(Number,City,wm_str,Wm) SELECT v_Number,p_city,'wm201403',wm201403 FROM flow_table WHERE Number=v_Number ; INSERT INTO flow_tmp(Number,City,wm_str,Wm) SELECT v_Number,p_city,'wm201404',wm201404 FROM flow_table WHERE Number=v_Number ; INSERT INTO flow_tmp(Number,City,wm_str,Wm) SELECT v_Number,p_city,'wm201405',wm201405 FROM flow_table WHERE Number=v_Number ; INSERT INTO flow_tmp(Number,City,wm_str,Wm) SELECT v_Number,p_city,'wm201406',wm201406 FROM flow_table WHERE Number=v_Number ; INSERT INTO flow_tmp(Number,City,wm_str,Wm) SELECT v_Number,p_city,'wm201407',wm201407 FROM flow_table WHERE Number=v_Number ; INSERT INTO flow_tmp(Number,City,wm_str,Wm) SELECT v_Number,p_city,'wm201408',wm201408 FROM flow_table WHERE Number=v_Number ; */ /*清除掉不數(shù)據(jù)=0的列*/ DELETE FROM csdn.flow_tmp WHERE Wm=0 OR Wm IS NULL; SELECT wm_str INTO v_start_wm FROM csdn.flow_tmp WHERE Number=v_Number ORDER BY wm_str ASC LIMIT 1; SELECT wm_str INTO v_end_wm FROM csdn.flow_tmp WHERE Number=v_Number ORDER BY wm_str DESC LIMIT 1; SELECT SUM(Wm) INTO v_num FROM csdn.flow_tmp WHERE Number=v_Number; END$$ DELIMITER ;
臨時(shí)表的所有數(shù)據(jù):
mysql> SELECT * FROM csdn.flow_tmp; +--------+----------+----------+--------+ | Number | City | wm_str | Wm | +--------+----------+----------+--------+ | 1 | shanghai | wm201403 | 100.20 | | 1 | shanghai | wm201404 | 180.40 | | 1 | shanghai | wm201405 | 141.00 | | 1 | shanghai | wm201406 | 164.00 | | 1 | shanghai | wm201407 | 124.00 | | 1 | shanghai | wm201408 | 127.00 | | 2 | shanghai | wm201403 | 110.23 | | 2 | shanghai | wm201404 | 180.34 | | 2 | shanghai | wm201405 | 141.23 | | 2 | shanghai | wm201406 | 104.78 | | 2 | shanghai | wm201407 | 124.67 | | 2 | shanghai | wm201408 | 127.45 | | 3 | beijing | wm201403 | 123.23 | | 3 | beijing | wm201404 | 110.34 | | 3 | beijing | wm201405 | 131.33 | | 3 | beijing | wm201406 | 154.58 | | 3 | beijing | wm201407 | 154.67 | | 3 | beijing | wm201408 | 167.45 | | 4 | hangzhou | wm201404 | 110.34 | | 4 | hangzhou | wm201405 | 131.33 | | 4 | hangzhou | wm201406 | 154.58 | | 4 | hangzhou | wm201407 | 154.67 | | 5 | hangzhou | wm201405 | 131.33 | | 5 | hangzhou | wm201406 | 154.58 | | 5 | hangzhou | wm201407 | 154.67 | +--------+----------+----------+--------+ 25 rows in set (0.00 sec) mysql>
統(tǒng)計(jì)每個(gè)用戶(hù)的使用總量為:
mysql> SELECT Number,SUM(Wm) 'total_num' FROM flow_tmp GROUP BY Number ORDER BY Number; +--------+-----------+ | Number | total_num | +--------+-----------+ | 1 | 836.60 | | 2 | 788.70 | | 3 | 841.60 | | 4 | 550.92 | | 5 | 440.58 | +--------+-----------+ 5 rows in set (0.00 sec) mysql>
USE csdn; DROP TABLE IF EXISTS csdn.tb; CREATE TABLE tb(`cname` VARCHAR(10),cource VARCHAR(10),score INT) ENGINE=INNODB; INSERT INTO tb VALUES('張三','語(yǔ)文',74); INSERT INTO tb VALUES('張三','數(shù)學(xué)',83); INSERT INTO tb VALUES('張三','物理',93); INSERT INTO tb VALUES('李四','語(yǔ)文',74); INSERT INTO tb VALUES('李四','數(shù)學(xué)',84); INSERT INTO tb VALUES('李四','物理',94); SELECT * FROM tb;
+--------------------+--------+--------+--------+-----------+--------------+
| 姓名 | 語(yǔ)文 | 數(shù)學(xué) | 物理 | 總成績(jī) | 平均成績(jī) |
+--------------------+--------+--------+--------+-----------+--------------+
| 張三 | 74.00 | 83.00 | 93.00 | 250.00 | 83.33 |
| 李四 | 74.00 | 84.00 | 94.00 | 252.00 | 84.00 |
| 總成績(jī)平均數(shù) | 74.00 | 83.50 | 93.50 | 251.00 | 83.67 |
+--------------------+--------+--------+--------+-----------+--------------+
SQL代碼塊如下:
SELECT cname AS "姓名", SUM(IF(cource="語(yǔ)文",score,0)) AS "語(yǔ)文", SUM(IF(cource="數(shù)學(xué)",score,0)) AS "數(shù)學(xué)", SUM(IF(cource="物理",score,0)) AS "物理", SUM(score) AS "總成績(jī)", ROUND(AVG(score),2) AS "平均成績(jī)" FROM tb GROUP BY cname UNION ALL SELECT "總成績(jī)平均數(shù)", ROUND(AVG(`語(yǔ)文`),2) , ROUND(AVG(`數(shù)學(xué)`),2), ROUND(AVG(`物理`),2), ROUND(AVG(`總成績(jī)`),2), ROUND(AVG(`平均成績(jī)`),2) FROM( SELECT "all",cname AS "姓名", SUM(IF(cource="語(yǔ)文",score,0)) AS "語(yǔ)文", SUM(IF(cource="數(shù)學(xué)",score,0)) AS "數(shù)學(xué)", SUM(IF(cource="物理",score,0)) AS "物理", SUM(score) AS "總成績(jī)", AVG(score) AS "平均成績(jī)" FROM tb GROUP BY cname )tb2 GROUP BY tb2.all;
執(zhí)行結(jié)果正確,如下所示:
+--------------------+--------+--------+--------+-----------+--------------+
| 姓名 | 語(yǔ)文 | 數(shù)學(xué) | 物理 | 總成績(jī) | 平均成績(jī) |
+--------------------+--------+--------+--------+-----------+--------------+
| 張三 | 74.00 | 83.00 | 93.00 | 250.00 | 83.33 |
| 李四 | 74.00 | 84.00 | 94.00 | 252.00 | 84.00 |
| 總成績(jī)平均數(shù) | 74.00 | 83.50 | 93.50 | 251.00 | 83.67 |
+--------------------+--------+--------+--------+-----------+--------------+
SQL代碼如下:
SELECT cname AS "姓名", MAX(CASE cource WHEN "語(yǔ)文" THEN score ELSE 0 END) AS "語(yǔ)文", MAX(CASE cource WHEN "數(shù)學(xué)" THEN score ELSE 0 END) AS "數(shù)學(xué)", MAX(CASE cource WHEN "物理" THEN score ELSE 0 END) AS "物理", SUM(score) AS "總成績(jī)", ROUND(AVG(score) ,2) AS "平均成績(jī)" FROM tb GROUP BY `cname` UNION ALL SELECT "總成績(jī)平均數(shù)", ROUND(AVG(`語(yǔ)文`),2) , ROUND(AVG(`數(shù)學(xué)`),2), ROUND(AVG(`物理`),2), ROUND(AVG(`總成績(jī)`),2), ROUND(AVG(`平均成績(jī)`),2) FROM( SELECT 'all' , cname AS "姓名", MAX(CASE cource WHEN "語(yǔ)文" THEN score ELSE 0 END) AS "語(yǔ)文", MAX(CASE cource WHEN "數(shù)學(xué)" THEN score ELSE 0 END) AS "數(shù)學(xué)", MAX(CASE cource WHEN "物理" THEN score ELSE 0 END) AS "物理", SUM(score) AS "總成績(jī)", ROUND(AVG(score) ,2) AS "平均成績(jī)" FROM tb GROUP BY `cname` )tb2 GROUP BY tb2.all
執(zhí)行結(jié)果正確,如下所示:
+--------------------+--------+--------+--------+-----------+--------------+
| 姓名 | 語(yǔ)文 | 數(shù)學(xué) | 物理 | 總成績(jī) | 平均成績(jī) |
+--------------------+--------+--------+--------+-----------+--------------+
| 張三 | 74.00 | 83.00 | 93.00 | 250.00 | 83.33 |
| 李四 | 74.00 | 84.00 | 94.00 | 252.00 | 84.00 |
| 總成績(jī)平均數(shù) | 74.00 | 83.50 | 93.50 | 251.00 | 83.67 |
+--------------------+--------+--------+--------+-----------+--------------+
SELECT IFNULL(cname,'總平均數(shù)') AS "姓名", MAX(CASE cource WHEN "語(yǔ)文" THEN score ELSE 0 END) AS "語(yǔ)文", MAX(CASE cource WHEN "數(shù)學(xué)" THEN score ELSE 0 END) AS "數(shù)學(xué)", MAX(CASE cource WHEN "物理" THEN score ELSE 0 END) AS "物理", ROUND(AVG(score),2) AS "總成績(jī)", ROUND(AVG(avg_score),2) AS "平均成績(jī)" FROM( SELECT cname , IFNULL(cource,'total') cource, SUM(score) AS score, ROUND(AVG(score) ,2) AS avg_score FROM tb GROUP BY `cname`,cource WITH ROLLUP HAVING cname IS NOT NULL )tb2 GROUP BY tb2.cname WITH ROLLUP;
mysql> SELECT IFNULL(cname,'總平均數(shù)') AS "姓名", -> MAX(CASE cource WHEN "語(yǔ)文" THEN score ELSE 0 END) AS "語(yǔ)文", -> MAX(CASE cource WHEN "數(shù)學(xué)" THEN score ELSE 0 END) AS "數(shù)學(xué)", -> MAX(CASE cource WHEN "物理" THEN score ELSE 0 END) AS "物理", -> ROUND(AVG(score),2) AS "總成績(jī)", -> ROUND(AVG(avg_score),2) AS "平均成績(jī)" -> FROM( -> SELECT -> Display ALL 793 possibilities? (Y OR n) -> cname , -> Display ALL 793 possibilities? (Y OR n) -> IFNULL(cource,'total') cource, -> Display ALL 793 possibilities? (Y OR n) -> SUM(score) AS score, -> Display ALL 793 possibilities? (Y OR n) -> ROUND(AVG(score) ,2) AS avg_score -> FROM tb -> GROUP BY `cname`,cource WITH ROLLUP HAVING cname IS NOT NULL -> )tb2 -> GROUP BY tb2.cname WITH ROLLUP; +--------------+--------+--------+--------+-----------+--------------+ | 姓名 | 語(yǔ)文 | 數(shù)學(xué) | 物理 | 總成績(jī) | 平均成績(jī) | +--------------+--------+--------+--------+-----------+--------------+ | 張三 | 74 | 83 | 93 | 125.00 | 83.33 | | 李四 | 74 | 84 | 94 | 126.00 | 84.00 | | 總平均數(shù) | 74 | 84 | 94 | 125.50 | 83.67 | +--------------+--------+--------+--------+-----------+--------------+ 3 ROWS IN SET, 1 warning (0.00 sec) mysql>
總結(jié): WITH rollup中對(duì)求列的總數(shù)是OK的,但是求列的平均數(shù)有偏差,這里場(chǎng)景使用不是恰當(dāng)。
SQL代碼塊如下:
/*僅僅班級(jí)成員部分*/ SET @a=''; SELECT @a:=CONCAT(@a,'SUM(IF(cource=\'',cource,'\'',',score,0)) AS ',cource,',') FROM (SELECT DISTINCT cource FROM tb) A; SET @a=CONCAT(@a,"ROUND(AVG(score) ,2) AS \"平均成績(jī)\""); SET @b=CONCAT('SELECT IFNULL(cname,\'總成績(jī)\'),',LEFT(@a,LENGTH(@a)-1),' ,SUM(score) AS \"總成績(jī)\" FROM tb GROUP BY cname '); /*班級(jí)成員總計(jì)部分**/ SET @a2=""; SET @b2=CONCAT('SELECT "all",IFNULL(cname,\'總成績(jī)\'),',LEFT(@a,LENGTH(@a)-1),' ,SUM(score) AS \"總成績(jī)\" FROM tb GROUP BY cname '); SELECT @a2:=CONCAT(@a2,'ROUND(AVG(`',cource,'`),2),') FROM (SELECT DISTINCT cource FROM tb) A; SET @a2=CONCAT(@a2," ROUND(AVG(`平均成績(jī)`),2),ROUND(AVG(`總成績(jī)`),2) "); SET @c=CONCAT("SELECT \"班級(jí)平均數(shù)\",",LEFT(@a2,LENGTH(@a)-1)," FROM(",@b2,")tb2 GROUP BY tb2.all;"); SET @d=CONCAT(@b," UNION ALL ",@c); PREPARE stmt1 FROM @d; EXECUTE stmt1;
查看執(zhí)行結(jié)果如下,已經(jīng)達(dá)到效果:
mysql> /*僅僅班級(jí)成員部分*/ mysql> SET @a=''; QUERY OK, 0 ROWS affected (0.00 sec) mysql> SELECT @a:=CONCAT(@a,'SUM(IF(cource=\'',cource,'\'',',score,0)) AS ',cource,',') FROM (SELECT DISTINCT cource FROM tb) A; +-----------------------------------------------------------------------------------------------------------------------------------+ | @a:=CONCAT(@a,'SUM(IF(cource=\'',cource,'\'',',score,0)) AS ',cource,',') | +-----------------------------------------------------------------------------------------------------------------------------------+ | SUM(IF(cource='語(yǔ)文',score,0)) AS 語(yǔ)文, | | SUM(IF(cource='語(yǔ)文',score,0)) AS 語(yǔ)文,SUM(IF(cource='數(shù)學(xué)',score,0)) AS 數(shù)學(xué), | | SUM(IF(cource='語(yǔ)文',score,0)) AS 語(yǔ)文,SUM(IF(cource='數(shù)學(xué)',score,0)) AS 數(shù)學(xué),SUM(IF(cource='物理',score,0)) AS 物理, | +-----------------------------------------------------------------------------------------------------------------------------------+ 3 ROWS IN SET (0.00 sec) mysql> SET @a=CONCAT(@a,"ROUND(AVG(score) ,2) AS \"平均成績(jī)\""); QUERY OK, 0 ROWS affected (0.00 sec) mysql> SET @b=CONCAT('SELECT IFNULL(cname,\'總成績(jī)\'),',LEFT(@a,LENGTH(@a)-1),' ,SUM(score) AS \"總成績(jī)\" FROM tb GROUP BY cname '); QUERY OK, 0 ROWS affected (0.00 sec) mysql> mysql> /*班級(jí)成員總計(jì)部分**/ mysql> SET @a2=""; QUERY OK, 0 ROWS affected (0.00 sec) mysql> SET @b2=CONCAT('SELECT "all",IFNULL(cname,\'總成績(jī)\'),',LEFT(@a,LENGTH(@a)-1),' ,SUM(score) AS \"總成績(jī)\" FROM tb GROUP BY cname '); QUERY OK, 0 ROWS affected (0.00 sec) mysql> SELECT @a2:=CONCAT(@a2,'ROUND(AVG(`',cource,'`),2),') FROM (SELECT DISTINCT cource FROM tb) A; +-----------------------------------------------------------------------+ | @a2:=CONCAT(@a2,'ROUND(AVG(`',cource,'`),2),') | +-----------------------------------------------------------------------+ | ROUND(AVG(`語(yǔ)文`),2), | | ROUND(AVG(`語(yǔ)文`),2),ROUND(AVG(`數(shù)學(xué)`),2), | | ROUND(AVG(`語(yǔ)文`),2),ROUND(AVG(`數(shù)學(xué)`),2),ROUND(AVG(`物理`),2), | +-----------------------------------------------------------------------+ 3 ROWS IN SET (0.00 sec) mysql> SET @a2=CONCAT(@a2," ROUND(AVG(`平均成績(jī)`),2),ROUND(AVG(`總成績(jī)`),2) "); QUERY OK, 0 ROWS affected (0.00 sec) mysql> SET @c=CONCAT("SELECT \"班級(jí)平均數(shù)\",",LEFT(@a2,LENGTH(@a)-1)," FROM(",@b2,")tb2 GROUP BY tb2.all;"); QUERY OK, 0 ROWS affected (0.00 sec) mysql> SET @d=CONCAT(@b," UNION ALL ",@c); QUERY OK, 0 ROWS affected (0.00 sec) mysql> mysql> PREPARE stmt1 FROM @d; QUERY OK, 0 ROWS affected (0.00 sec) Statement prepared mysql> EXECUTE stmt1; +---------------------------+--------+--------+--------+--------------+-----------+ | IFNULL(cname,'總成績(jī)') | 語(yǔ)文 | 數(shù)學(xué) | 物理 | 平均成績(jī) | 總成績(jī) | +---------------------------+--------+--------+--------+--------------+-----------+ | 張三 | 74.00 | 83.00 | 93.00 | 83.33 | 250.00 | | 李四 | 74.00 | 84.00 | 94.00 | 84.00 | 252.00 | | 班級(jí)平均數(shù) | 74.00 | 83.50 | 93.50 | 83.67 | 251.00 | +---------------------------+--------+--------+--------+--------------+-----------+ 3 ROWS IN SET (0.00 sec) mysql>
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