Test database downloaded on github. Index: explain select: query the scope of the date field of the employees table if you want to query the recruits in a certain period of time, 1. Why interpret the results, using the type field or ALL? What doe...
b-tree structure if the name field is an index, then if there are seven pieces of data in the table, all nodes in the b-tree also have seven pieces of data, so isn t scanning the entire data area as efficient as scanning the entire index area? ...
the database currently has 1 million data (it has been running for about half a month) the following sentence takes 6 seconds to run (1 million results for where alone), and both user_id and time are indexed ...
reference article: Innodb lock mechanism: Next-Key Lock talk about-jyzhou-blog Park Why should Next-Key Lock be designed as a left open and right closed interval? Can t be designed as a gap lock? Why is right closed? ask the boss to answer. < ...
The question originates from this article: MySQL answering questions using filesort VS using temporary in the article: mysql> explain select * from t1 force index(id), t2 where t1.id=1 and t1.col1 = t2.col2 order by t2.col1 ; +----+-------------...
I have seen a lot of articles on mysql indexes that say that if a field has a small range of values (a large number of duplicate values), there is no need to establish an index. but my actual test: user_type_id field has an index: then executi...
this is the definition of the index in the MySQL table recommendation in Alibaba s Java development manual, where: the primary key index is named pk_ field name isn t an index created for the primary key by default? how do you name this index? ask B...
for example, I always thought that select * from table where index column = xx and AMISOM column = yy must take the index of index column. but today I found that is not the case . tested (MySQL 5.6.16): when the union condition can match to th...
MySQL table with the following structure CREATE TABLE `t_article` ( `id` bigint(20) unsigned NOT NULL AUTO_INCREMENT, `content` varchar(255) NOT NULL COMMENT , `like_count` int(10) unsigned NOT NULL DEFAULT 0 COMMENT , PRIMARY KEY (...
< H1 > as shown in the title: < H1 > EXPLAIN execution Plan: the following is my table structure. It takes 7 seconds to query more than 10, 000 pieces of data. CREATE TABLE order_copy ( id bigint (20) NOT NULL AUTO_INCREMENT, seq_id bigint...
< H1 > description < H1 > first of all, there is a table with a table structure of CREATE TABLE `article_like` ( `id` int(10) unsigned NOT NULL AUTO_INCREMENT COMMENT id , `article_id` int(10) unsigned NOT NULL COMMENT id , `user_id` int(...
can mysql set different weights for different fields when building a full-text index? For example, if you have fields with title and content, you want the weight of title to be higher than that of content ....
problem description there is a user table with in it. uid regdate reg_package reg_channel ... now I have a SQL query for user data SELECT * FROM `user` ORDER BY `regdate` DESC LIMIT 0,50; there is a multi-column index on this table. i...
there are two tables Table 1: Student number 1 | Student number 2 | Student number 3 001 | 002 | 003 Table 2: Student number | name 001 | Zhang San 002 | Li Si 003 | Wang Wu desired results: student number 1 | name 1 | student number 2 | nam...
problem description take over a new database, today found table data 50G, and then various indexes 75G, of which three large indexes are each around 23g, and most of the large indexes are bound to timestamps. what result do you expect? What is the e...
CREATE TABLE test1 ( id int (11) NOT NULL AUTO_INCREMENT, name varchar (20) DEFAULT NULL, code varchar (50) DEFAULT NULL, PRIMARY KEY ( id ), KEY idx_code ( code ) CREATE TABLE test2 ( id int (11) NOT NULL AUTO_INCREMENT, name varc...
tinyint that has been used before for fields that represent data types or states has not paid attention to the bit type. After consulting the data, we know that bit is stored in binary format: bounded 0 or bounded 1 its storage unit is direc...
when querying, you need to query the scope according to the time field, timestamp type. Statement does not have subqueries, associated queries, only look up this table. it takes about 4.5 seconds to find 50, 000 results. This field has been indexed, bu...
when there are too many SQL pages (for example, limit 1000000,20), the efficiency will be significantly reduced. How to optimize it? Here, take mysql as an example ...
background and phenomena the amount of data in the report_product_sales_ data table is 28 million; it has been tested that when the, order by primary key id,limit reaches 49 under the current data volume, the PRIMARY primary key index can be used w...