Does mysql have json type?
mysql has json type. Starting from version 5.7, MySQL has introduced the JSON data type, which can directly manipulate json data; but below MySQL version 5.7, you need to rely on data types such as varchar or text to store data in JSON format in tables. The JSON type in MySQL json is a very useful data type in mysql5. Before 7, people used strings to store json, but there is a problem that json cannot be manipulated. After 5.7, json data can be directly manipulated. There is nothing to say about creating json. The length is 0 by default Update and insert can be inserted with string Query, personally don’t like to use The data is handed over to the background for processing, so let’s hand it over to the database. The example is as follows: A table in the database has a content_json field, which contains such data! { “bill”: [ { “bill”: [ { “id”: “C81AEAD03F90000142E81B405F6FADC0”, “uuid”: “cfd872541b3b4507a50c2b2eda6bef28”, “billid”: “kjdzyljgmzsfzypj”, “pageno”: [], “billver”: “V1”, “billname”: “New Test”, “fjNumber”: “”, “trueName”: “”, “allPageno”: [ { “top”: 13, “left”: 7 } ], “billValue”: {}, “isOtherZL”: “”, “billNumber”: “”, “fjTMNumber”: “” }, { “id”: “C81AED69D6400001A07818551D9EBEC0”, “uuid”: “05d87c8052cd44209c684407d200b7ec”, “billid”: “opztsfpsgd”, “pageno”:…
How does mysql delete multiple tables in batches?
How to delete multiple tables in batches in mysql: Use the “DROP TABLE” statement, just write the table names one after the other, separated by commas; the grammar format “DROP TABLE [IF EXISTS] Table name 1 [ , table name 2, table name 3 …]”. mysql> SHOW TABLES; +——————–+ |Tables_in_test_db| +——————–+ |tb_emp1| |tb_emp2| |tb_emp3| +——————–+ 2 rows in set (0.00 sec) It can be seen from the running results that there are 3 data tables tb_emp1, tb_emp2 and tb_emp3 in the database. Let’s delete the data tables tb_emp1 and tb_emp3, the entered SQL statement and the running results are as follows: mysql> DROP TABLE tb_emp1 ,tb_emp3; Query OK, 0 rows affected (0.22 sec) mysql> SHOW TABLES; +——————–+ |Tables_in_test_db| +——————–+ |tb_emp2| +——————–+ 1 rows in set (0.00 sec) As you can see from the execution results, the tables named tb_emp1 and tb_emp3 no longer exist in the data table list of the test_db database, and the deletion operation is successful. Recommended tutorial: mysql video tutorial The above is how mysql deletes multiple tables in batches? For more details, please pay attention to other related articles on 1024programmer.com!
How does mysql insert multiple pieces of data?
How to insert multiple pieces of data in mysql: 1. Use the “INSERT INTO table name field list VALUES (value 1) … , (value n);” statement to insert data; 2. Use “INSERT INTO table name SET Field 1 = value 1, field 2 = value 2,…” statement inserts data. INSERT INTO [ [ , … ] ] VALUES (value 1) [… , (value n) ]; The syntax is explained as follows. : Specify the name of the table to be operated. : Specify the column name that needs to insert data. If you want to insert data into all columns in the table, all column names can be omitted, just use INSERT VALUES(…) directly. VALUES or VALUE clause: This clause contains a list of data to be inserted. The order of the data in the data list should correspond to the order of the columns. 2) INSERT…SET statement The syntax format is: INSERT INTO SET = , = , … This statement is used to directly specify the corresponding column values for certain columns in the table, that is, the column name of the data to be inserted is specified in the SET clause, col_name is the specified column name,…
How to install mysql graphical tool on mac?
How to install the mysql graphical tool on mac: first download the installation file of the mysql graphical tool Navicat Premiun; then click the downloaded dmg file, drag it to the application folder for installation, and follow the instructions on the installation guide interface step by step Just step by step. （3）If the connection is unsuccessful and the error message client does not support authentication protocol requested by server consider …, please continue to read the error solution A. The terminal connects to mysql 【mysql -u root -p】 B. The terminal enters the following statement, remember to change the password in the statement to your own mysql connection password. [ALTERUSER 'root'@'localhost' IDENTIFIED WITH mysql_native_password BY 'password';] C, terminal input refresh statement [FLUSH PRIVILEGES; 】 Reconnect, success, error resolution. ending—–Remember to like it Recommended tutorial: mysql video tutorial The above is the mac installation mysql graphical tool? For more details, please pay attention to other related articles on 1024programmer.com!
How to change the installation path of Mysql?
How to change the installation path of Mysql: When installing Mysql, select “Custom Installation” in the installation guide interface; then select the mysql file to be downloaded; then change the path, click the “Advanced Options” button, in the pop-up You can customize the installation path of mysql and the directory of Data in the window. Recommended tutorial: mysql video tutorial The above is how to change the installation path of Mysql? For more details, please pay attention to other related articles on 1024programmer.com!
Can mysql set a joint unique index?
mysql can set the joint unique index, method: use the “Alter table table name add UNIQUE index index name (field 1, field 2)” statement to set, it will delete duplicate records, keep one, and then create Joint unique index. joint unique index The project needs to add a unique index to a certain two fields of a table , to ensure that the values of these two fields cannot be duplicated at the same time. Alter table table name add UNIQUE index index name (field 1, field 2) When duplicate data already exists in the table , an error will be reported when adding, and the data needs to be deduplicated. 1. Check out the duplicate data first SELECT * FROM (SELECT field, COUNT(1 ) AS num FROM table GROUP BY field) temp WHERE num > Delete manually. 2.Alter ignore table table name add UNIQUE index index name (field 1, field 2) It will delete duplicate records (one will be kept ), and then create a unique index, which is efficient and user-friendly (not tested). I also found some related content: 1. Add PRIMARY KEY (primary key index) ALTER TABLE `table_name` ADD PRIMARY KEY ( `column` ) 2. Add UNIQUE…
How does mysql query the data of a field in the database?
How to query a certain field in the database in mysql: use the SELECT statement, use the “SELECT FROM ;” syntax to query; if you want to query multiple fields, use different field names Separate them with a comma “,”. In MySQL, you can use the SELECT statement to query data. Querying data refers to using different query methods to obtain different data from the database according to requirements, which is the most frequently used and most important operation. The syntax of SELECT is as follows: SELECT {* | } [ FROM , … [WHERE [GROUP BY [HAVING [{ }…]] [ORDER BY ] [LIMIT[,] ] ] Among them, the meaning of each clause is as follows: {*| } A field list containing asterisk wildcards, indicating the name of the field to be queried. , …, Table 1 and Table 2 indicate the source of query data, which can be single or multiple. WHERE is optional, if you select this item, the query data must meet the query condition. GROUP BY, this clause tells MySQL how to display the queried data and group it by the specified field. [ORDER BY], this clause tells MySQL in what order to display the queried…
How does mysql query two tables?
Mysql two-table query method: 1. Use “select field list from table 1, table 2 [where condition]” to query; 2. Use “SELECT field list FROM table 1 keyword JOIN table 2 ON Table1.Field = Table2.Field;” to query. How does mysql query two tables? The following article will introduce to you the method of multi-table query in mysql. There is a certain reference value, and friends in need can refer to it, and I hope it will be helpful to everyone. Multi-table joint query #Create table and data # create department CREATE TABLE IF NOT EXISTS dept ( did int not null auto_increment PRIMARY KEY, dname VARCHAR(50) not null COMMENT ‘Department Name’ )ENGINE=INNODB DEFAULT charset utf8; #Add department data INSERT INTO `dept` VALUES ('1', 'teaching department'); INSERT INTO `dept` VALUES ('2', 'Sales Department'); INSERT INTO `dept` VALUES ('3', 'Marketing Department'); INSERT INTO `dept` VALUES ('4', 'Personnel Department'); INSERT INTO `dept` VALUES ('5', 'Dept of Encouragement'); — Creator DROP TABLE IF EXISTS `person`; CREATE TABLE `person` ( `id` int(11) NOT NULL AUTO_INCREMENT, `name` varchar(50) NOT NULL, `age` tinyint(4) DEFAULT '0', `sex` enum('Male','Female','Shemale') NOT NULL DEFAULT 'Shemale', `salary` decimal(10,2) NOT NULL DEFAULT '250.00', `hire_date` date NOT NULL, `dept_id` int(11) DEFAULT NULL, PRIMARY KEY (`id`)…
How to modify mysql database table?
How to modify the mysql database table: Use the “ALTER TABLE” statement to change the structure of the original table, such as adding or deleting fields, modifying the original field data type, renaming the field or table, modifying Table character set, etc.; syntax “ALTER TABLE [modify options]”. The premise of modifying the data table is that the table already exists in the database. Modifying a table refers to modifying the structure of an existing data table in the database. The operation of modifying the data table is also indispensable in database management. Just like drawing a sketch, you can use an eraser to erase too much drawing, and add it with a pen if you have less drawing. If you don’t know how to modify the data table, it is equivalent to throwing away and redrawing as long as you make a mistake, which increases unnecessary costs. In MySQL, you can use the ALTER TABLE statement to change the structure of the original table, such as adding or deleting columns, changing the original column type, renaming columns or tables, etc. The syntax format is as follows: ALTER TABLE [modify option] modify option The syntax format is as follows: { ADD…
How does mysql clear and delete tables?
The method of clearing the table in mysql: use the “TRUNCATE table name” statement to completely clear a table; the method of deleting the table: use “DROP TABLE table name 1 [ , table name 2, table name 3 . ..];” statement. mysql empty table MySQL provides DELETE and TRUNCATE keywords to delete the data in the table. The TRUNCATE keyword is used to completely empty a table. Its syntax format is as follows: TRUNCATE [TABLE] table name The TABLE keyword can be omitted. Example Create a new table tb_student_course, insert data and The query, SQL statement and running result are as follows: mysql> CREATE TABLE `tb_student_course` ( -> `id` int(4) NOT NULL AUTO_INCREMENT, -> `name` varchar(25) NOT NULL, -> PRIMARY KEY (`id`) -> ); Query OK, 0 rows affected (0.04 sec) mysql> INSERT INTO tb_student_course(name) VALUES ('Java'),('MySQL'),('Python'); Query OK, 3 rows affected (0.05 sec) Records: 3 Duplicates: 0 Warnings: 0 mysql> SELECT * FROM tb_student_course; +—-+——–+ | id | name | +—-+——–+ | 1 | Java | | 2 | MySQL | | 3 | Python | +—-+——–+ 3 rows in set (0.00 sec) Use the TRUNCATE statement to clear the records in the tb_student_course table, the SQL statement…
