摘要:富士康小心,前方有坑返回的結果默認是無序的,即不會按照距離遠近進行排序。需要手動加上進行排序。
1、查找表中多余的重復記錄,重復記錄是根據單個字段(peopleId)來判斷
select * from people where peopleId in (select peopleId from people group by peopleId having count(peopleId) > 1)
2、刪除表中多余的重復記錄,重復記錄是根據單個字段(peopleId)來判斷,只留有一個記錄
delete from people where peopleId in (select peopleId from people group by peopleId having count(peopleId) > 1) and min(id) not in (select id from people group by peopleId having count(peopleId )>1)
3、查找表中多余的重復記錄(多個字段)
select * from vitae a where (a.peopleId,a.seq) in (select peopleId,seq from vitae group by peopleId,seq having count(*) > 1)
4、刪除表中多余的重復記錄(多個字段),只留有rowid最小的記錄
delete from vitae a where (a.peopleId,a.seq) in (select peopleId,seq from vitae group by peopleId,seq having count(*) > 1) and rowid not in (select min(rowid) from vitae group by peopleId,seq having count(*)>1)
5、查找表中多余的重復記錄(多個字段),不包含rowid最小的記錄
select * from vitae a where (a.peopleId,a.seq) in (select peopleId,seq from vitae group by peopleId,seq having count(*) > 1) and rowid not in (select min(rowid) from vitae group by peopleId,seq having count(*)>1)
6.mysql delete刪除關聯多表數據
DELETE reviews,reviews_description FROM reviews LEFT JOIN reviews_description ON reviews.reviews_id=reviews_description.reviews_id WHERE reviews.status="0"
7.mysql delete in操作
delete from sns_hits where id not in (select id from another_table) delete from sns_hits where id not in (select id from sns_hits)# error CREATE TEMPORARY TABLE tmp_sns_hits ( `id` BIGINT(20) ) DELETE FROM t_tag WHERE id NOT IN (SELECT * FROM (SELECT MAX(t .id) AS id FROM t_tag t GROUP BY tagname)t)
8.一對多查詢
select ID from 表2 where (select CONCAT(",", ksort , ",")AS ksort from 表1 ) LIKE CONCAT("%,", ID , ",%"); from [Mysql刪除重復記錄](http://blog.baitongda.cn/article/119)
9.group by先排序后分組,group by默認的是第一條記錄,相同的iID的記錄不會先進行排序再group by
select from (select from t where 你的查詢條件 order by 你的排序字段) group by 你的分組字段
10.mysql case when
SELECT count(enq_id) AS total, sum(purchase_amount) AS purchase FROM temp_stock WHERE purchase_date <> "0000-00-00" AND purchase_date < "2012-08-01" AND ( STATUS = "Sold" OR STATUS = "In Stock" OR STATUS = "Ref") AND CASE STATUS WHEN "Sold" THEN delivery_date >= "2012-08-01" ELSE 1=1 END SELECT * FROM logs WHERE pw="correct" AND CASE WHEN id<800 THEN success=1 ELSE 1=1 END AND YEAR(TIMESTAMP)=2011 WHERE pw="correct" AND (id>=800 OR success=1) AND YEAR(timestamp)=2011 WHERE pw="correct" AND CASE WHEN id<800 THEN success=1 ELSE TRUE END AND YEAR(timestamp)=2011
mysql where case when
--簡單Case函數 CASE sex WHEN "1" THEN "男" WHEN "2" THEN "女" ELSE "其他" END --Case搜索函數 CASE WHEN sex = "1" THEN "男" WHEN sex = "2" THEN "女" ELSE "其他" END
mysql 排序去重 sql 寫法
| data_id | user_id | data_name |hits | 1 | 2 | test1 | 140 | 2 | 2 | test2 | 200 | 3 | 3 | test2 | 110 | 4 | 3 | test2 | 10 | 5 | 1 | test2 | 130 | 6 | 4 | test2 | 10 | 7 | 4 | test2 | 100 查詢出來下面的 3 條結果,也就是前 3 條點擊量最多的數據, user_id 不能重復 SELECT t.* FROM ( SELECT user_id, max(hits) AS max_hits FROM t GROUP BY user_id ) t2 LEFT JOIN t ON t.user_id = t2.user_id AND t.hits = t2.max_hits ORDER BY t2.max_hits DESC LIMIT 3 | data_id | user_id | data_name |hits | 2 | 2 | test2 | 200 | 5 | 1 | test2 | 130 | 3 | 3 | test2 | 110
order by 出現數據錯誤問題
select `stock`.*, `stock1`.`price_current` as `price_current1`, `stock1`.`rank` as `rank1`, `stock`.`price_current` - `stock1`.`price_current` as `percent1` from `stock` inner join `stock` as `stock1` on `stock`.`code` = `stock1`.`code` and `stock`.`date` = "2016-10-10" and `stock1`.`date` = "2016-09-30" and `stock`.`code` = "600817" order by `percent1` descG price_current 這個字段設置了 UNSIGNED ,用 order by 會生成臨時表,而臨時表也就會同樣是 UNSIGNED ,這就導致所有percent1為負值的都變成 0.00 了
MYsql 去重復語句
delete from `xxx` where id in (select * from (SELECT min(id) FROM `xxx` group by mail having count(mail)>1) as a); create table tmp_xxx select min(id) as id,mail,password from xxx group by mail,password; 只保留一條不重復數據 DELETE T FROM MYTABLE T LEFT JOIN (SELECT MAX(A.ID) AS ID FROM MYTABLE A GROUP BY A.MAIL) TT ON T.ID = TT.ID WHERE TT.ID IS NULL 刪除重復數據中的一條 DELETE T FROM MYTABLE T LEFT JOIN (SELECT MIN(A.ID) AS ID FROM MYTABLE A GROUP BY A.MAIL HAVING COUNT(A.MAIL) > 1) TT ON T.ID = TT.ID WHERE TT.ID IS NOT NULL MySQL 唯一索引和插入重復自動更新 INSERT INTO table (id, user_id, token) VALUES (NULL, "2479031", "232") ON DUPLICATE KEY UPDATE user_id = VALUES(user_id), token = VALUES(token), online = VALUES(online) user_id 是唯一索引字段,如果 insert 的時候該 user_id 已經存在,那么就將觸發更新而不是插入,此時相當于執行了 update table set user_id = 2479031 token = 232 where user_id = 2479031 mysql導入大批量數據出現MySQL server has gone away的解決方法 http://blog.csdn.net/fdipzone/article/details/51974165 source /tmp/user.sql mysql> show global variables like "max_allowed_packet"; +--------------------+---------+ | Variable_name | Value | +--------------------+---------+ | max_allowed_packet | 4194304 | +--------------------+---------+ mysql> set global max_allowed_packet=268435456; 使用set global命令修改 max_allowed_packet 的值,重啟mysql后會失效,還原為默認值。 如果想重啟后不還原,可以打開 my.cnf 文件,添加 max_allowed_packet = 256M 即可 查看當前使用的配置文件my.cnf的方法 locate my.cnf mysql啟動時加載這個配置文件 ps aux|grep mysql|grep "my.cnf" 如果沒有設置使用指定目錄的my.cnf,mysql啟動時會讀取安裝目錄根目錄及默認目錄下的my.cnf文件。 mysql --help|grep "my.cnf" 在mysql默認讀取的目錄中,創建一個my.cnf文件(例如:/etc/my.cnf),把需要修改的配置內容寫入,重啟mysql后即可生效 You can"t specify target table for update in FROM clause錯誤的解決方法 不能在同一個sql語句中,先select同一個表的某些值,然后再update這個表 mysql> update message set content="Hello World" where id in(select min(id) from message group by uid); 解決方法:select的結果再通過一個中間表select多一次,就可以避免這個錯誤 update message set content="Hello World" where id in( select min_id from ( select min(id) as min_id from message group by uid) as a ); Mysql select 中嵌套帶子句https://www.v2ex.com/t/318573 SELECT tt.*,u.name,(SELECT group_concat(title) FROM tag WHERE id IN (tt.tag)) as tag FROM content tt LEFT JOIN user u ON tt.owner=u.id ORDER BY ts_created DESC SELECT tt.*,u.name,(SELECT group_concat(title) FROM tag WHERE FIND_IN_SET(id,tt.tag)) as tag FROM content tt LEFT JOIN user u ON tt.owner=u.id ORDER BY ts_created DESC 分組 select p.id,p.productname,p.productcode,p.price,l.num from p left join (select pid, sum(num) as num from wlms_stock group by pid) l on p.id = l.pid 從表2中獲得每個pid的總數sum(num),然后用pid跟表1去連接,這樣就既能獲得表1的所有數據也能獲得表2中的總數了https://segmentfault.com/q/1010000005941808 獲取 用戶最近10條文章 和 回復的文章https://segmentfault.com/q/1010000007169518 (SELECT id,title,create_time,"article" as type FROM fb_articles WHERE user_id = 4) UNION (SELECT a.id,a.title,b.create_time,"reply" as type FROM fb_articles as a,fb_replys as b WHERE a.id = b.article_id AND b.user_id = 4) ORDER BY create_time DESC LIMIT 10 SELECT * FROM(SELECT user_id,title,create_time FROM article UNION ALL SELECT user_id,article_id,create_time FROM reply) ar WHERE ar.user_id=xxx ORDER BY create_time desc LIMIT 10 MySQL 中將 varchar 字段轉換成數字進行排序 將 attr_price 轉換為數字再進行排序, *1 即可 "ORDER BY a.sort_order, g.attr_price * 1, g.goods_attr_id"; order by cast(col as unsigned)這會把小數位去掉,不合理 查詢并更新到另個表的字段update 表 a inner join 表1 b set a.Nums = b.rcmd_count where a.id = b.id數據庫返回的整型數據被偷換成了字符串類型
問題出在了 PHP 的 MySQL 驅動上 http://stackoverflow.com/ques...
http://stackoverflow.com/ques...
更新 PHP 的 MySQL 驅動
sudo apt-get update
sudo apt-get install php5-mysqlnd
編輯 my.cnf, 注意,需置于 mysqld 的 section 下 log_slow_queries = /tmp/mysql-slow.log long_query_time = 2 重啟 mysql. 只有 insert, update, delete 慢 set profiling=1; SHOW PROFILES; show profile for query 1;使用 Redis GeoHash 實現附近的XXX
這里 sicily 類似山東省,而 Palermo, Catania 類似煙臺、威海,即 Palermo、Catania 是 sicily 轄區內的城市。 redis> GEOADD Sicily 13.361389 38.115556 "Palermo" 15.087269 37.502669 "Catania" (integer) 2 redis> GEODIST Sicily Palermo Catania "166274.15156960039" redis> GEORADIUS Sicily 15 37 100 km 1) "Catania" redis> GEORADIUS Sicily 15 37 200 km 1) "Palermo" 添加時,經度在前,維度在后。 GEORADIUSBYMEMBER yeda "富士康" 1 km 小心,前方有坑! 返回的結果默認是無序的,即不會按照距離遠近進行排序。需要手動加上 ASC, DESC 進行排序。 GEORADIUSBYMEMBER yeda "富士康" 10 km WITHDIST ASC 如何在 Laravel 中使用 composer require predis/predis $items = Redis::georadius("yeda", $lng, $lat, 20, "km", "WITHDIST", "ASC"); 2) "Catania"MySQL 崩潰導致 Discuz! Database Error (2002) notconnect 錯誤
innodb_buffer_pool_size 的默認值,在 5.5 之后就被調成了 128M, 參考最新的 mysql 5.5, 5.6 文檔
在 my.conf 中將這個 buffer 調小
innodb_buffer_pool_size=32M
Redis監控方法redis-cli info
獲取Redis所有Key的方法:
1.終端
獲取所有Key命令:redis-cli keys ‘*’ ;
獲取指定前綴的key:redis-cli KEYS “edu:*”
如果需要導出,可以redis-cli keys ‘*’ > /data/redis_key.txt
刪除指定前綴的Key redis-cli KEYS “edu:*” | xargs redis-cli DEL
2.PHP獲取Redis所有Key
獲取Redis所有Key:$keys = $redis->keys(‘*’);
獲取指定前綴的Key:$keys = $redis->keys(‘edu*’);
刪除指定前綴的Key :$redis->delete($redis->keys(‘image*’));
mysql遞歸查詢https://segmentfault.com/q/1010000007523914 select id,name,pid from (select *from user order by pid,id) a,(select @pv := "8") init where (find_in_set(pid,@pv)>0) and @pv := concat(@pv,",",id) or id = 8; mysql> delimiter // mysql> mysql> CREATE FUNCTION `getChildLst`(rootId INT) -> RETURNS varchar(1000) -> BEGIN -> DECLARE sTemp VARCHAR(1000); -> DECLARE sTempChd VARCHAR(1000); -> -> SET sTemp = "$"; -> SET sTempChd =cast(rootId as CHAR); -> -> WHILE sTempChd is not null DO -> SET sTemp = concat(sTemp,",",sTempChd); -> SELECT group_concat(id) INTO sTempChd FROM treeNodes where FIND_IN_SET(pid,sTempChd)>0; -> END WHILE; -> RETURN sTemp; -> END -> // Query OK, 0 rows affected (0.00 sec) mysql> delimiter ; mysql> select * from treeNodes -> where FIND_IN_SET(id, getChildLst(1)); +----+----------+------+ | id | nodename | pid | +----+----------+------+ | 1 | A | 0 | | 2 | B | 1 | | 3 | C | 1 | | 4 | D | 2 | | 5 | E | 2 | | 6 | F | 3 | | 7 | G | 6 | +----+----------+------+ 7 rows in set (0.01 sec)mysql分組
$res = ["2016-11-18","2016-11-19"]; $s=implode("","",$res);//"2016-11-18","2016-11-19" echo """.$s.""";//""2016-11-18","2016-11-19"" $sql="select date_format(created,"%Y-%m-%d") as date,count(*) from test where date_format(created,"%Y-%m-%d") in ("".$s."") group by date order by id desc limit 5;"mysql優化查詢速度
select id from t where num=10 or num=20
select id from t where num=10
union all
select id from t where num=20
select num from a where num in(select num from b)
select num from a where exists(select 1 from b where num=a.num)
直接分析慢查詢文件
pt-query-digest slow.log > slow_report.log
分析最近12小時內的查詢
pt-query-digest --since=12h slow.log > slow_report2.log
update table_name set field_name = CASE id WHEN id1 THEN field_value, WHEN id1 THEN field_value END一個 MySQL 用戶名長度的坑
MySQL user names can be up to 32 characters long (16 characters before MySQL 5.7.8). http://dev.mysql.com/doc/refm...
grant all privileges on . to joe@10.163.225.87 identified by ‘123′;
find_in_set單條記錄沒問題,比如唯一id的in。多條記錄order會失效select * from act_log where answer in ("B","C","CD") order by find_in_set( answer,""B","C","CD"")
排序錯誤:CD,C,BB,C
select * from tb1 order by a desc ,id desc limit 3; 用limit和order by 一個非唯一字段時,結果集并不總是確定的.已經確定為bughttp://www.codesec.net/view/2...
select SUM(fee) AS income, SUM(IF(type=5, fee, 0)) AS reward
1、可以先把數據按照你的條件要求,使用order by排好序
2、在查詢sql外面,再包一層查詢,使用group by
例如: select from (select from t where 你的查詢條件 order by 你的排序字段) group by 你的分組字段
(1)單個字段如果大于65535,則轉換為TEXT 。
(2)單行最大限制為65535,這里不包括TEXT、BLOB
查詢一個月當中每個人每天的第一次和最后一次記錄SELECT MIN(card_time) AS mintime, MAX(card_time) AS maxtime , user_sn, card_date FROM testtbl GROUP BY user_sn, card_date
數據庫去除重復記錄insert into xxxx (select xxx from xxxx)
然后再 delete from xxx where id in (select xxx from xxxx)
新建表,數據復制到新表然后 rename 切換 http://www.cnblogs.com/wangta...
按ID降序排序,如果用戶狀態為0(未激活),則注冊時間升序,排在結果最后select *from user order by status desc,case status when 1 then id end desc,case status when 0 then created_at end asc;
過濾 三個字段 有重復的記錄select * FROM tt t1, tt t2 WHERE t1.userid = t2.userid and t1.pid = t2.pid and t1.tid = t2.tid and s1.id != s2.id
查詢total_time > 100SELECT *
FROM tuanke_time
LEFT JOIN tuanke_student ON tuanke_student.Sid = tuanke_time.studentID
GROUP BY tuanke_time.studentID having SUM(tuanke_time.time) > 100;
select user,num from (select * from tb order by time asc) as a group by a.user;
刪除重復記錄DELETE FROM price_monitor WHERE id NOT IN ( SELECT * FROM ( SELECT MAX(id) FROM price_monitor GROUP BY domain ) as tmp )limit sum
select uid, sum(skip) as sumskip, time from (select uid, skip, time from attendance where uid = 8499 order by time limit 3) as subt;
mysql刪除大量數據,直接delete會鎖表DELIMITER $$ CREATE PROCEDURE delete_temp_tab() BEGIN REPEAT DELETE FROM test.`tab` WHERE id > 111352 LIMIT 1000; UNTIL ROW_COUNT()=0 END REPEAT; END $$ DELIMITER ; CALL delete_temp_tab(); DROP PROCEDURE IF EXISTS delete_temp_tab;mysql 分頁查詢優化
EXPLAIN SELECT `id` FROM `table` WHERE `node` = 2 ORDER BY `create_at` DESC LIMIT 12 OFFSET 69996 #查詢1 SELECT `id` FROM `table` WHERE `node` = 2 ORDER BY `id` ASC LIMIT 10 查詢第二頁的SQL如下 SELECT `id` FROM `table` WHERE `node` = 2 AND `id`>10 ORDER BY `id` ASC LIMIT 10每次取10000 三次取完
分塊 $sql = "SELECT xxx FROM table WHERE xxx LIMIT limit :limit offset :offset"; $limit = 10000; $offset = 0; do{ $stmt = $dbh->prepare($sql, array(PDO::ATTR_CURSOR => PDO::CURSOR_FWDONLY)); $stmt->execute(array(":limit" => $limit, ":offset" => $offset)); $data = $stmt->fetchAll(); // 處理邏輯 $offset += $limit; }while(count($data)); 游標,按行讀取返回 $sql = "SELECT xxx FROM table WHERE xxx"; $stmt = $dbh->prepare($sql, array(PDO::ATTR_CURSOR => PDO::CURSOR_SCROLL)); $stmt->execute(); $row = $stmt->fetch(PDO::FETCH_NUM, PDO::FETCH_ORI_LAST); do { // 處理邏輯 $row } while ($row = $stmt->fetch(PDO::FETCH_NUM, PDO::FETCH_ORI_PRIOR));正則匹配手機號前綴
SELECT name FROM users WHERE phone REGEXP "^15[1-4]";
redis setbitsetbit key offset,其中offset用userid取代,如果ID為1的用戶是男性就setbit key 1 1,
如果是女性就setbit key 1 0,獲取ID為1的性別就getbit key 1
在沒有索引的情況下,我會采用先delete后insert。
但在有索引的情況下,我會采用以下方式先update后insert
delimiter $$ CREATE PROCEDURE test() begin declare begintime int(10); set begintime = unix_timestamp("2016-7-31 23:59:59"); loop1:LOOP IF begintime > unix_timestamp("2016-9-30 23:59:59") then leave loop1; END IF; select * from tablename where timestamp between begintime and begintime+1800; set begintime = begintime + 1800; END LOOP loop1; end;$$子查詢不支持limit
SELECT * FROM yi_user_joke WHERE id in (SELECT id FROM yi_user_joke WHERE status="2" ORDER BY audit_time desc LIMIT 499950,10 ) ORDER BY audit_time desc LIMIT 10 ; ERROR 1235 (42000): This version of MySQL doesn"t yet support "LIMIT & IN/ALL/ANY/SOME subquery" SELECT * FROM yi_user_joke a inner join (SELECT id FROM yi_user_joke WHERE status="2" ORDER BY audit_time desc LIMIT 499950,10 ) as b on a.id=b.id ORDER BY a.audit_time desc LIMIT 10 ; SELECT * FROM yi_user_joke WHERE id in (select *from (SELECT id FROM yi_user_joke WHERE status="2" ORDER BY audit_time desc LIMIT 499950,10 ) as b) ORDER BY audit_time desc LIMIT 10 ;分組取前五
select * from table as a where (select count(distinct(total)) from table as b where a.stage_id = b.stage_id and b.total > a.total) < 5;where中的select是保證遍歷所有記錄,取每條記錄與當前記錄做比較,只有當table表中同一stage_id不超過5個人total當前選擇item的total高時,這個item就算是每組total排行的前5名查詢每個部門工資前3名
select * from table d1 where (select count(*) from table d2 where d2.bumen=d1.bumen and d2.salary>d1.salary) < 3 order by d1.salary desc
從一個表中選出最后幾個元素SELECT * FROM ( SELECT * FROM tmp_table ORDER BY id DESC LIMIT 50 ) sub ORDER BY id ASC 選出分組求和的平均數SELECT AVG(sum_column1) FROM (SELECT SUM(column1) AS sum_column1) FROM t1 GROUP BY column1) AS t1;group by
group by 是用于分組統計的,會按照分組字段進行排序,如果 order by 和 group by 同時出現,order by 是對 group by 的結果排序,因此取的是根據 group by 排序后各組第一條,但這是有邏輯錯誤的,好像只有在 MySQL 中可行。 這句 SQL 就好比一個班級的女生按照寢室分組,然后你想知道分組的結果屬于誰? 其實誰都不屬于,但你可以得到每個組中屬性的最大值,最小值,或者具有分組統計意義的信息。 從 MySQL 5.7.5 起,SELECT 不在 GROUP BY 中的字段將會導致數據庫拒絕執行查詢 order by 只有后面跟著 limit 在子查詢才有意義 select * from (select * from table order by <字段 2> limit 1000) as temp group by <字段 1>
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