Above function work for concate multiple columns : CONCAT This function is used to concatenate multiple columns or strings into a single one. The method arguments are separated by a comma. Syntax – CONCAT( column1, column2, … ) OR CONCAT ( string1, string2, … ) MySQL Query to Concate...
...: 根据学生姓名分组; 在每个分组内,使用 CASE WHEN 语句根据课程名称动态生成一列新的值; 使用 MAX() 函数筛选出每个分组中的最大值,并命名为对应的课程名称; 将结果按照学生姓名进行聚合返回...方法二:使用 GROUP_CONCAT 函数 除了第一种方法,也可以使用 GROUP_CONCAT() 函数和 SUBSTRING_INDEX() 函数...
8.3.5 Multiple-Column Indexes MySQL can create composite indexes (that is, indexes on multiple columns). An index may consist of up to 16 columns. For certain data types, you can index a prefix of the column (seeSection 8.3.4, “Column Indexes”). ...
MySQL can create composite indexes (that is, indexes on multiple columns). An index may consist of up to 16 columns. For certain data types, you can index a prefix of the column (see Section 8.3.4, “Column Indexes”). MySQL can use multiple-column indexes for queries that test all th...
create database crashcourse default character set utf8mb4 collate utf8mb4_general_ci; # 创建指定的数据库(指定字符集和排序规则) use crashcourse; # 指定使用的数据库 show databases; # 了解数据库,返回数据库列表 show tables; # 返回数据库内表的列表 show columns from customers; # 查看customers表...
multiple commands, continue even if an error occurs. -C, --compress Use compression in server/client protocol. --character-sets-dir=name Directory for character set files. --default-character-set=name 设置字符集. -?, --help Display this help and exit. ...
The server is executing the first part of a multiple-table delete. It is deleting only from the first table, and saving columns and offsets to be used for deleting from the other (reference) tables. deleting from reference tables The server is executing the second part of a multiple-table...
· 错误:1241 SQLSTATE: 21000 (ER_OPERAND_COLUMNS) 消息:操作数应包含%d列。 · 错误:1242 SQLSTATE: 21000 (ER_SUBQUERY_NO_1_ROW) 消息:子查询返回1行以上。 · 错误:1243 SQLSTATE: HY000 (ER_UNKNOWN_STMT_HANDLER) 消息:指定给%s的未知预处理语句句柄。 · 错误:1244 SQLSTATE: HY000 (ER_...
SELECT class,name,CAST(GROUP_CONCAT( CONCAT(subject,' ',test1, ' ',test2) SEPARATOR ' '),char) AS data FROM t.exam GROUP BY name,class; PB http://www.artfulsoftware.com Subject Written By Posted Splitting the column value into multiple columns ...
Also read groups with concat(group, suffix) (Supported in all NDB releases based on MySQL 5.7) --help, -? Display help text and exit (Supported in all NDB releases based on MySQL 5.7) --lock=#, -l # Lock type (Supported in all NDB releases based on MySQL 5.7) ...