use pymysql to connect to mysql database and extract data. If the amount of data is more than 500000 +, the speed is relatively slow. I d like to ask about the ways to speed up in addition to optimizing sql statements. here I use pd.read_sql, directly...
now we need to first judge whether a row of data is in the data table, update if it exists, insert if it doesn t exist, but when there are more than 2000 rows of data that need to perform such business logic, I find that the efficiency is very low, wh...
there seems to be no difference between the two SQL implementations. select * from A left join B on A.aid=B.aid where A.aid=100 select * from ( select * from A where A.aid=100 ) AA left join B on AA.aid=B.aid what do you think of SQL performing ...
there is a problem. What should I do if I want to take a record that matches multiple characters in a field? select * from actor where last_name like ( % DAVI% , MOSTEL% , ABC , kkk%aa ) the above sql statement is incorrect. Like does not sup...
as shown in the figure: intend to visit the server IP to view the database and code PS:wamp ...
I want to sort each person s type in descending order according to the sum of the sl of each person s sl. What should I do with ...
what is the cause of this situation, and how to solve SELECT o.order_id, o.send_goods_status send_goods_status, FROM ( SELECT o.order_id, mi.STATUS send_goods_status, FROM ypb_order_info o LEFT JOIN ypb_order_merc...
is like this, and the ultimate effect is to match the avatar address of the drink in the user table for each comment list first, query out the table_1 (article comment table) article comment result set then I found that these comments do not have...
can you give me a column? ...
SELECT * FROM `table_1` WHERE `reply_parent` IN (SELECT `reply_id` FROM (SELECT `reply_id` FROM `table_1` WHERE `reply_article`=69 AND `reply_type`=0 LIMIT 0, 5)AS t) UNION (SELECT * FR...
(SELECT * FROM `dozhan_reply` t1 WHERE `reply_parent` IN ( SELECT `reply_id` FROM ( SELECT `reply_id` FROM `dozhan_reply` WHERE `reply_article` = 69 AND `reply_type` = 0 LIMIT 0, 5 ) t )) UNION (SEL...
data table test has the following data {name: a , parent_key: 1,value: 11}, {name: b , parent_key: 3,value: 12}, {name: c , parent_key: 3,value: 13}, {name: d , parent_key: 3,value: 14}, {name: e , parent_key: 2,value: 15}, {name: f ...
take MySQL as an example, what is the difference (principle and efficiency) between in and exists and between not in and not exists? What about using indexes? Say that not in and < > will not use indexes, won t you? ...
The < H1 > grouping includes testers, developers, and customer service personnel. Now you need to obtain the members under the grouping to integrate other information. I only found users under users, but I couldn t find any other fields to correspond to...
this is my Structure (system) table Standard the relationship between the two tables is that the StructureID of the Standard table is equal to the Id field of the Structure now I want to find out all the criteria of the Id below 7 and all the c...
means there is no train of thought at all. if user An is only in the R & D group and id is 5, then the number after user An is 32 . How should I write this sentence? There is no external network. I don t know if I can see the pictures taken by pri...
my statement is select user_vip_card . , flow_of_vipcard . , if ((user_vip_card.max_times IS NULL OR user_vip_card.max_times= 0 OR user_vip_card.max_times=9999),-1, (user_vip_card.max_times-count (flow_of_vipcard.id) AS remain_times ...
is there any way? such as recommended books, blogs, etc. ...
Name Class Score Zhang San Chinese 81 Zhang San Mathematics 75 Li Si Chinese 76 Li Si Mathematics 90 Wang Wu Chinese 81 Wang Wu Mathematics 100 Wang Wu English 90 use a SQL sentence to query the Name of the students with the lowest Chinese sco...
download PostgreSQL10.3 and open pg4Admin and then flicker or fail to open the default browser when you report an error. I tried to uninstall and reinstall many times without solving it, but the SQL Shell interface is available. tried to download va...
can the front end imitate my Alipay app drag-and-drop? Find the solution long press to move and adjust position. I use the sortable.js plugin , but I can t drag and drop it on my phone . var el = document.getElementById( items ) ...
I currently have a query using mongodb3.4, that needs to be paged. Paging needs to return the total number and number of pages. but that s the problem. Paging queries are fast, but counting is slow . The count statement is as follows: db.message.fin...
problem description use in vue how to pass token values into url using Query String Parameters when sending axios requests the environmental background of the problems and what methods you have tried related codes Please paste the code text ...
linux cPP uses socket to simulate receiving http requests, and socket blocking does not set a timeout. When a get request for the same http is initiated with Firefox,chrome,IE under Windows or Linux, it only takes about 100 microseconds for recv to compl...
1, According to the official rabbitmq documentation, we set up a test to create a queue and send messages to receive messages, but they are all executed in the form of php server.php and php client.php. If deployed to a server, how to implement client.ph...