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Mysql query questions, according to the latest published articles or the latest comments to query the information of the first few users.
tb_user (user information) id tb_article (article information) id, foreign key user_id-> tb_user.id tb_comment (comment information) id, foreign key user_id-> tb_user.id query the top 5 users of the latest article or comment. order by tb_article.cre...
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Lock table under Mysql Innodb:RR level. Why write blocks select? in another transaction
I ran lock table employees write, on one transaction and then used select statements on another transaction, without for update or lock in share mode
select is said to be snapshot read, unlocked, why it is lock table. Write watch lock blocking?
...
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The mysql root account seems to be messed up.
two questions, when logging in, typing mysql-u root-p correctly jumps to the password line, but you can t type the password on the keyboard. You can t log in with a password, but you can log in directly by typing mysql. Is this the wrong place? I have...
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How do I enter a null value when navicat operates on mysql?
I want to change the place shown in the picture to null
...
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How to insert data including single quotation marks, double quotation marks, and back quotation marks into the mysql?
if the data to be saved contains "`, how can it be inserted into the database? A rookie, please give me some advice. ...
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JAVA inserts MySQL data exception
jav inserts Mysql data exception Data too long
exception information
2018-04-24 00:15:01 ERROR com.comall.cybershop.common.base.DaoSupport
org.springframework.dao.DataIntegrityViolationException: PreparedStatementCallback; SQL [update cs_awardCardRe...
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I would like to ask mysql added group by after other indexes invalidated, how to solve?
EXPLAIN SELECT
s.id,
s.name,
s.price,
s.unit,
s.qty,
s.remark,
s.image,
s.cuft,
s.volume,
s.status,
s.vender_id AS venderId,
s.booth_id AS boothId,
s.booth_no AS boothNo,
s.show_booth_no AS showBoothNo,
s.name_en AS nameEn,
...
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The problem of compound Primary key in MySQL
Today we have a problem with a compound primary key, which ensures that multiple column combinations are not unique. But in practice, it s the opposite.
this is my table structure
12342,2,1:
wonder
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When installing mysql with brew, no matter what password you change, you will be prompted for this.
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Is this a problem with the MySQL driver version?
using myql-connector-java5.0.8 jar package to connect to the database of MySQL 5.7.22, the following error occurred
Exception in thread "main " java.sql.SQLException: No suitable driver found for jdbc:mysql:192.168.31.218:3306 school
at java.sql.Dri...
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Mysql insert operation lost part of the field value, how to solve?
this is the case. Recently, when there is an occasional Mysql insert operation in the system, some field data of a record is lost. When I check the printed sql statement, there is a value, such as
: .
before the insert operation, I output the attri...
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Add or remove indexes for online data tables
as in the question, when I add or remove indexes for a table in the database, I have two choices
use alter table to change the table structure
use the create drop index command
Which of these two methods is better? What I want to consider is, if ...
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The difference between QPS and TPS
such as the title. I searched the Internet for answers, but I still didn t get it (in fact, all the answers are the same, which makes me speechless). And ask the great gods here for advice. ...
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Oracle stored procedure, after adding a variable, why did you report this error?
CREATE OR REPLACE PROCEDURE QD_MYDTJ
(BEGINDATE VARCHAR2,
ENDDATE VARCHAR2,
xz_name VARCHAR2,
xz_number VARCHAR2,
--BEGININTEVAL VARCHAR2,
--ENDINTEVAL VARCHAR2,
start1 IN NUMBER,
limit1 IN NUMBER,
AN_O_RET_CODE ...
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Spring transaction, update has an exception rollback problem in the loop?
in a transactional method, by reading a collection of table records and cycling the values of update or save fields, the administrative account is updated every time an ordinary account is updated. so re-query the system account .
@Transactional(rollba...
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How does node+mysql, generate the following shopping cart interfaces (array package objects), such as the following figure and code
< H2 > problem, want to find out a data set similar to Taobao shopping cart < H2 >
A user has a shopping cart, there are multiple stores under one shopping cart, and there are multiple items under one store linked table query 1. Check out the shop...
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The default value of SpringBoot Jpa MySql field is CURRENT_TIMESTAMP invalidation
problem description
I created a table in the mysql database, one of which is the CURRENT_TIMESTAMP, of the default value of the field create_time. I added a new piece of data when I did the hope test in the project. The project uses the SpringBoot f...
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Unknown process gpg
problem description
the proportion of gpg,CPU of an unknown process encountered on the database server is high. I am not sure whether it has anything to do with the database. I am not sure whether it has anything to do with the database. I did not dar...
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What does it mean not to use foreign keys in Internet development?
it is said that Internet developers try to not to use foreign keys , so what does the here mean by not using foreign keys ? 1. The meaning here is clear: No foreign key constraints . For example, when deleting data in one table, if you want to casc...
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Under the separation of mysql read and write, is, select for update/lock in share mode performed in the read library or the write library?
under the separation of mysql read and write, is, select for update lock in share mode performed in the read library or the write library? ...
