Intersection: an element that appears at least twice in all setsUnion: combine the elements of multiple sets and remove the duplicate elementsDifference set: an element that exists in the first set and does not exist in other sets
commandexplainsinter key [key ...]Gets the intersection of all setssinterstore desiti ...
Posted by KoopaTroopa on Sun, 22 May 2022 02:45:39 +0300
hash type and operation
The hash type in Redis can be understood as a map container with String Key and String Value, so the hash type is suitable for storing value object information. Such as Username, Password or Age. Even if there are only a few fields in the hash, its data only takes up a small amount of disk space. Each ha ...
Posted by daniel_grant on Sat, 21 May 2022 04:01:06 +0300
1. DML - modify operation
2. DML delete
3. Mysql simple query operation
4. Multi table relationship and table building principle
4. Mysql multi table Association query
4.1 mysql Association query classification
4.2 write sql statement to realize mysql multi table Association query
5. Mysql query operation
1. DM ...
Posted by drag0n on Fri, 20 May 2022 23:14:59 +0300
Introduction: This paper will mainly introduce the process and related parameters of reading and writing Clickhouse by FlinkX. The core content will focus on the following three questions: 1 Which version does FlinkX Clickhouse support 2. What are the parameters for Clickhouse to read and write Clickhouse 3. What are the instructions for Clickh ...
Posted by pedroz on Fri, 20 May 2022 16:16:32 +0300
Generally, some record tables of the business system have some uniqueness constraints. For example, duplicate names are not allowed under the same user; You can usually create a unique index on the specified column, for example:
CREATE TABLE `novel`
`id` bigint(20 ...
Posted by JayBachatero on Fri, 20 May 2022 14:36:13 +0300
Building your own website is one of the signs of success as a coder,
Then there are other signs of success, holding Bai Fumei in your left hand, rolling a small barbecue in your right hand, and stepping on Santana under your feet
Some children will say, uncle fish, aren't you designing a database table? How do you return the p ...
Posted by kingcobra96 on Fri, 20 May 2022 09:38:56 +0300
1. Conditional test operation
(1) document test[file or directory]-d: Whether the directory is directory (test) -e: Test whether the directory or file exists (Exist) -f: Test whether it is a file -r: Test whether the current user has permission to read, -w: Test whether the current user has permission to write -x: T ...
1, jdbc connection to mysql above 8.0
After the mysql version above 8.0 is updated, the corresponding jdbc connection has also changed.
First of all, we need to configure the mysql environment. It is recommended that you go to the Internet to find a tutorial and follow it. I won't talk about the installation and configuration of mysql here.
Posted by mjl4975 on Fri, 20 May 2022 03:06:37 +0300
1, Environmental installation
The first is the installation of MySQL, which is directly installed only with apt get command (this method is recommended here, because it does not need to link the relevant path when compiling later programs)
sudo apt-get install mysql-server
After my installation, the relevant header files and dynamic lib ...
Posted by posidon on Fri, 20 May 2022 01:31:35 +0300