MySQL enterprise development specification

MYSQL Development specification arrangement

• All database object names must be lowercase and separated by underscores （MySQL Case sensitive , The name should see the meaning of the name , Better not exceed 32 character ）

• It is forbidden to store pictures in data , File binary data （ Use a file server ）

• Do not do database stress tests online

• Forbidden from development environment , The test environment is directly connected to the production environment database

• Limit the number of indexes on each table , It is recommended that the index of a single table should not exceed 5 individual （ Indexing increases query efficiency , But it will reduce the speed of insertion and update ）

• Avoid using ENUM data type （ modify ENUM Values need to be used ALTER sentence ,ENUM Type of ORDER BY Low operating efficiency , Require additional operations , It is forbidden to use book value as ENUM The enumerated values

• Try to define all fields as NOT NULL（ Indexes NULL Need extra space to save , So you need to use more memory temporarily , The comparison and calculation should be correct NULL It's worth special treatment ）

• Use timestamp or datetime Type to store time

• Financial related amount data , use decimal type （ No loss of accuracy , No use float and double）

• All database object names are prohibited MySQL Reserved keyword

• The temporary library table must be in the form of tmp Is prefixed and suffixed with a date （tmp_）

• Backup libraries and libraries must be bak Is prefixed and suffixed with a date (bak_)

• All column names and column types that store the same data must be consistent .

• The character set of database and table should be used uniformly as much as possible utf8（ The character set must be uniform , Avoid garbled code caused by character set conversion , Chinese characters utf8 Take up 3 Bytes ）

• All tables and fields should be annotated COMMENT, Maintain the data dictionary from the beginning

• It is recommended to manage big data by physical tables

• Try to separate hot and cold data , Reduce the width of the table （mysql Limit maximum storage 4096 Column , There is no limit to the number of lines , However, the total number of bytes per line cannot exceed 65535. Column restriction benefits ： Reduce disk io, Ensures a memory cache hit ratio for hot data , Avoid reading useless cold data ）

• It is forbidden to create a reserved field in a table （ Unable to confirm stored data type , Modify the reserved field type , Will lock the table ）

• Avoid using double % Number and like, It is strictly forbidden to search for left blur or full blur （ If necessary, please use search engine to solve . Index file has B-Tree The leftmost prefix matching property of , If the value on the left is not determined , Then this cable cannot be used ）

• Precompiled statements are recommended for database operations

• Cross database query is prohibited （ Leave room for data migration and database and table segmentation , Reduce coupling , Reduce risk ）

• prohibit select * Inquire about （ Consume more cpu and io And network bandwidth resources , Cannot use overlay index ）

• in Avoid if operation can be avoided , If it can't be avoided , Need to be evaluated carefully in Number of set elements behind , Control in 1000 Within

• No use order by rand（） Sort at random

• Avoid creating redundant and duplicate indexes （ redundancy ：index（a,b,c) index(a,b) index(a)）

• It is forbidden to create a separate index for each column in a table

• The most distinguished column is placed on the leftmost side of the union index

• Try to put columns with small field lengths on the far left of the union index

• Try to avoid using foreign keys （ Prohibit the use of physical foreign keys , Logical foreign keys are recommended ）

• Use as much as possible union all Instead of union

• Split complex large SQL For the multiple small SQL（ MySQL One SQL You can only use one CPU Calculate ）

• For the program to connect to the database account , Follow the principle of minimum authority

• More than three tables prohibited join.（ need join Field of , Data types must be absolutely consistent ; When multi table associated query , Ensure that the associated field needs to have an index . Even if the double meter join Also pay attention to table indexes 、SQL performance .）

• stay varchar When indexing on a field , Index length must be specified , There's no need to index all fields , Determine the index length according to the actual text differentiation .

• SQL Objectives of performance optimization ： At the very least range Level , The requirement is ref Level , If it could be consts best

• Use ISNULL() To determine whether it is NULL value .

• Try not to use physical deletion （ Delete directly , If you want to delete it, make a backup in advance ）, It's using logical deletion , Use fields delete_flag Do logical deletion , The type is tinyint,0 Indicates not deleted ,1 Indicates that

• If there is order by Scene , Note the use of index order .order by The last field is the combination , Part of index , And put it at the end of the index combination order , Avoid file_sort The situation of , Affect query performance .