explain select * from tb_user force index(idx_user_pro) where profession = '软件工程'; 示例演示: A. use index explain select * from tb_user use index(idx_user_pro) where profession = '软件工程'; B. ignore index explain select * from tb_user ignore index(idx_user_pro) where professi...
sqlite>select*fromtb_user; 设置输出列的宽度 1 2 sqlite> .width 10, 20, 10 sqlite>select*fromtb_user; SQLite 的 ORDER BY 子句是用来基于一个或多个列按升序或降序顺序排列数据。 基本语法:SELECT column-list FROM table_name [WHERE condition] [ORDER BY column1, column2, .. columnN] [ASC ...
sql只是一个字符串变量这句话的意思只是将一串字符串赋给sql,并没有具体的查询操作,没有实际含义和 a= "b" 没有本质区别查询表tb_user的所有记录，返回所有字段赋给sql是利用sql打开数据库连接把一个查询字符串赋值给变量Sql，
sqlite> select * from tb_user; 1. 2. SQLite 的 ORDER BY 子句是用来基于一个或多个列按升序或降序顺序排列数据。 基本语法:SELECT column-list FROM table_name [WHERE condition] [ORDER BY column1, column2, .. columnN] [ASC | DESC]; sqlite> select * from tb_user order by name asc; -...
mysql> select * from users; 2、指定字段 mysql> select uname,department,email from users where id>2; +---+---+---+ | uname | department | email | +---+---+---+ | lily | tech | lily@foxmail.com | | sum | tech | sum@qq.com | | jim | ...
使用escape,转义字符后面的%或_就不作为通配符了,注意前面没有转义字符的%和_仍然起通配符作用 select username from gg_user where username like '%xiao/_%' escape '/'; select username from gg_user where username like '%xiao/%%' escape '/'; 在like 里面为了查找 “\”,必须指定它为 “\\\”...
C++使用mysql判断select查询结果是否为空/mysql_query返回值问题 MYSQL sqlcon; string str = "SELECT * FROM dt_user where user...{ return true; } mysql_query的返回值,无效sql语句的时候会返回false,但如果输入sql语句时有效的,仍然会返回有效的id,换句话说mysql_query无论是否查询值...while ((row = ...
sqlite> select userid,username from tb_user;格式化的查询输出 sqlite> .header on sqlite> .mode column sqlite> select * from tb_user;设置输出列的宽度 sqlite> .width 10, 20, 10 sqlite> select * from tb_user;SQLite 的 ORDER BY 子句是用来基于一个或多个列按升序或降序顺序排列数据。基本语法...
Any of FE host export FE_HOST='selectdb-cn-***.selectdbfe.rds.aliyuncs.com' # http_port in fe.conf export FE_HTTP_PORT=8080 # query_port in fe.conf export FE_QUERY_PORT=9030 # Doris username export USER='admin' # Doris password export PASSWORD='***' # The database where TPC-...
Any of FE host export FE_HOST='selectdb-cn-***.selectdbfe.rds.aliyuncs.com' # http_port in fe.conf export FE_HTTP_PORT=8080 # query_port in fe.conf export FE_QUERY_PORT=9030 # Doris username export USER='admin' # Doris password export PASSWORD='***' # The database where TPC-...