Define Type I error in simple words. Explain why making a type 1 error is more serious than a type 2 error. Describe type I and type II errors of a mammography in terms of the diagnosis. When do a type I error
mysql>EXPLAINFORMAT=JSONSELECTname, quantityFROMordersJOINitems iONitem_id = i.idWHEREquantity >1000\G { "query_block": { "select_id":1, "cost_info": { "query_cost":"49827.84" }, "nested_loop": [ { "table": { "table_name":"orders", "ac...
customNum=100 orderNum=200 rm tmp rm custom.sql for i in `seq $customNum`; do uuid=$(uuidgen) echo $uuid >> tmp done ## custom.sql文件为向t_custom表插入数据的sql awk -v LINE_NUM=$customNum 'BEGIN{ srand(); for(i=1;i<=LINE_NUM;i++) { a[i]=int(rand()*10000%100); ...
explain的作用: 判断mysql语句执行的时间效率分析;1、在navicate客户端使用sql语句的时候,整体图形如下2、名词解释 一、select_type数据列指明各“单位select查询”的查询类型,select_type数据列的列值如下所示:1.simple:进行不需要Union操作或不含子查询的简单select查询时,响应查询语句的 ...
EXPLAIN (FORMAT YAML) SELECT * FROM foo WHERE i='4'; QUERY PLAN --- - Plan: + Node Type: "Index Scan" + Scan Direction: "Forward"+ Index Name: "fi" + Relation Name: "foo" + Alias: "foo" + Startup Cost: 0.00 + Total Cost: 5.98 + Plan Rows: 1 + Plan Width: 4 + Index...
关于explain执行计划,下列哪些说法是正确的: A. type列显示了连接使用了何种类型,从最好到最差的连接类型为:const,eq_ref,ref,range,i
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CREATE TABLE t(i INT) ENGINE=MYISAM; INSERT INTO t VALUES(1); EXPLAIN SELECT * FROM t 存储引擎的统计数据是精确的,意思是例如MyISAM存储存储引擎有记录的记录的个数 system是性能最高的情况 而如果再添加一条记录,会变为all,而InnoDB即使一条数据也是all 于此同时,INNODB访问count()的数据也是all的 CRE...
(255) DEFAULT ''; DECLARE i INT DEFAULT 0; WHILE i < n DO SET return_str =CONCAT(return_str,SUBSTRING(chars_str,FLOOR(1+RAND()*52),1)); SET i = i + 1; END WHILE; RETURN return_str; END // DELIMITER ; SET GLOBAL log_bin_trust_function_creators=1; #创建存储过程: DELIMITER...
SET i = i + 1; END WHILE; RETURN return_str; END // DELIMITER ; SET GLOBAL log_bin_trust_function_creators=1; #创建存储过程: DELIMITER // CREATE PROCEDURE insert_s1 (IN min_num INT (10),IN max_num INT (10)) BEGIN DECLARE i INT DEFAULT 0; SET autocommit = 0; REPEAT SET i...