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First, create a databaseMysql> CREATE database company;mysql> use company;Second, create a table1. Create a table officesMysql> CREATE TABLE Offices , Officecode Int (ten) not NULL UNIQUE, city varchar (+) not NU LL, address varchar (+)

Set and enum data types are all string objects.Set can contain up to 64 elements, and any element in the set can be obtained. However, enum can only obtain one Wood Element in the set, which can contain a maximum of 65536 elements. That is to say,

What are the differences among KEY, primary key, unique key, and INDEX in MySQL? mysqlunique You can split the questions raised in the questions to solve them step by step. In MySQL, KEY and INDEX are synonymous. This problem can be simplified to

Mysql summary. The explain statement is mainly used for select queries in SQL statements. it can display the index hits of the SQL statement, so as to better utilize the index and optimize the query efficiency. The Explain syntax is as follows:

MySQL index analysis and optimization indexes are used to quickly search for records with specific values. all MySQL indexes are saved as B-trees. If no index exists, MySQL must scan all the records of the entire table from the first record until

This is a creation in Article, where the information may have evolved or changed. Some things about the recent company spec database, the old program told me that NULL is not allowed in MySQL, that columns with null values cannot be indexed and have

This article mainly introduces the method of modifying the table structure in mysql, and analyzes in detail the methods and precautions for modifying the table structure in mysql in the form of instances, which has some reference value, for more

MYSQlleftjoin union query efficiency analysis user table: Id | name---1 | libk2 | zyfon3 | daodao User_action table: User_id | action-----1 | jump1 | kick1 | jump2 | run4 | swim SQL:Select id, name, action from user as uLeft join user_action a on u.

CREATETABLE [dbo]. [Jqfk] ([id] [int] IDENTITY (1, 1) NOTNULL, [yhh] [char] (13) NULL, CREATETABLE [dbo]. [Jqfk] ([id] [int] IDENTITY (1, 1) NOTNULL, [yhh] [char] (13) NULL, [cbrq] [nvarchar] (19) NULL, [ysl] [int] NULL,) [cbrq] [nvarchar] (19) NULL

Some tips on MySQL (continuous update) bitsCN. com1. use RAND () to extract random rows in MySQL. the method for generating random numbers is the RAND () function. you can use this function together with the order by clause to perform random row

MySQL string function usage instructions bitsCN.com usually uses the entire string as the operation object, such: search for a substring in a substring, obtain a substring, insert a substring at a certain position in the substring, and delete a

This article mainly introduces the primary key in MySQL and the usage tutorial for setting auto-increment. it is the basic knowledge in MySQL getting started. if you need it, refer 1. primary key declaration method:You can add a primary key to the

This article mainly introduces the simple optimization tutorial for table connection query in MySQL. table connection query is one of the most common basic operations in MySQL, so its optimization is also worth noting, for more information, see a

My experiences in MYSQL (8) my experiences in MYSQL (8) My experiences with MYSQL (1) My experiences with MYSQL (2) My experiences with MYSQL (III) My experiences with MYSQL (4) My experiences with MYSQL (5) My experiences with MYSQL (6) My

MySQL learning footprint record 02-SELECT bitsCN.com MySQL learning footprint record 02-SELECT Table structure and data used in this query mysql> SHOW COLUMNS FROM products; +------------+--------------+------+-----+---------+-------+| Field

Getting started with MYSQL: basic database and table operations bitsCN.com Step 8: basic database and table operations Related links: MYSQL: Basic operations Http: // database/201212/173868 .html MYSQL 2: use regular expressions to search Http: //

Each line of command uses a semicolon (;) as the end. For MySQL, the first line must be kept in mind that each line of command uses a semicolon (;) as the end, however, when a line of MySQL is inserted in PHP code, it is best to omit the semicolon.

MySQL provides standard SQL mode matching and an extended regular expression mode matching format based on Unix utilities such as vi, grep, and sed. MySQL provides standard SQL mode matching and an extended regular expression mode matching format

Primary Key altertabletabelnameaddnew_field_idint (5) unsigneddefa0notnullauto_increment, addprimarykey (new_fi // Primary key alter table tabelname add new_field_id int (5) unsigned default 0 not null auto_increment, add primary key (new_fi

After pythonmysqlplug-In fails conn.exe cute (,), you need to add the following sentence: conn. commit () is required for transaction processing, which is not mentioned in many places .. I don't know how their code works- After the python mysql