unique_subquery:不容易遇见,in 后面跟子查询,查询优化器将in转换为exists子查询,且这些自查徐你可以使用到主键进行等值匹配才可以。如explain select * from table1 where field in (select id from table2 where talbe1.fieldn = 'string') or field2 = 'string' index_subquery:使用子查询的结果作为索引来...
unique_subquery:不容易遇见,in 后面跟子查询,查询优化器将in转换为exists子查询,且这些自查徐你可以使用到主键进行等值匹配才可以。如explain select * from table1 where field in (select id from table2 where talbe1.fieldn = 'string') or field2 = 'string' index_subquery:使用子查询的结果作为索引来...
EXPLAIN SELECT * FROM s1 WHERE key1 IN (SELECT key1 FROM s2); #子查询被转为了物化表 # 4. partition(略):匹配的分区信息 # 5. type:针对单表的访问方法 #当表中`只有一条记录`并且该表使用的存储引擎的统计数据是精确的,比如MyISAM、Memory, #那么对该表的访问方法就是`system`。 CREATE TABLE ...
表中只有一行数据或者是空表,这是const类型的一个特例。且只能用于myisam和memory表。如果是Innodb引擎表,type列在这个情况通常都是all或者index 2、const 最多只有一行记录匹配。当联合主键或唯一索引的所有字段跟常量值比较时,join类型为const。其他数据库也叫做唯一索引扫描 ...
id INT PRIMARY KEY AUTO_INCREMENT, name VARCHAR(50) NOT NULL, price FLOAT NOT NULL ) ENGINE=InnoDB DEFAULT CHARSET=utf8; CREATE TABLE orders ( id INT PRIMARY KEY AUTO_INCREMENT, user_id INT NOT NULL, order_date DATETIME NOT NULL, ...
In the execution plan, the bottom table is the table that is used to create a hash table. Optimization suggestion: Update statistics The core idea is to use the small table to create a hash table. If a large table is used to create a hash table in the memory, more resources are con...
Cause: A column in the query is not found in the summary. To obtain the column, a join back of materialized view to the table by means of either the primary key, foreign key or rowid of the table is required. The specified materialized view does not have the primary key, foreign key...
Another difference between serverless and the normal vCore model of Azure SQL Database is that with serverless you can specify a minimum and maximum number of vCores. Memory and I/O limits are proportional to the range that is specified. ...
watermark=[-(rowtime, 1000:INTERVAL SECOND)]]], fields=[symbol, price, tax, rowtime], changelogMode=[I]): rowcount = 1.0E8, cumulative cost = {1.0E8 rows, 1.0E8 cpu, 4.0E9 io, 0.0 network, 0.0 memory} advice[1]: [WARNING] Unsupported to resolve non-deterministic issue in match-reco...
Each output rowfrom EXPLAIN provides information about one table. Each row contains the valuessummarized in Table 7.1, “EXPLAIN Output Columns”, and described in more detailfollowing the table. --MySQL 执行计划的输出选项如下表所示: 下面具体看看每项的含义: ...