ALTERTABLEtable_nameADDcolumn_name datatype --例如该员工表添加一列员工邮箱: altertablePeopleaddPeopleMail nvarchar(100) (2)如需在表中删除列,请使用下面的语法: ALTERTABLEtable_name DROPCOLUMNcolumn_name --例如删除员工表中的邮箱这一列 altertablePeople dropcolumnPeopleMail (3)如需改变表中列的数据...
The SQL CREATE TABLE statement is the SQL command that adds a new table to an SQL database. Tables are a basic unit of organization and storage of data in SQL. Each table tends to represent an entity such as a customer, product, code or event. A table is similar to a file in a ...
The examples use the basic syntax. For more complex examples, see Use Sparse Columns and Use Column Sets. This example creates a table that has a sparse column. SQL Copy CREATE TABLE dbo.T1 ( c1 INT PRIMARY KEY, c2 VARCHAR (50) SPARSE NULL ); This example creates a table that has...
以下语句使用NTH_VALUE()函数查找薪水第二高的员工: CREATE TABLE basic_pays( employee_name VARCHAR(50) NOT NULL, department VARCHAR(50) NOT NULL, salary INT NOT NULL, PRIMARY KEY (employee_name , department) ); INSERT INTO basic_pays(employee_name, department, salary) VALUES ('Diane Murphy',...
DROP TABLE IF EXISTS `ent_basic`;CREATE TABLE `ent_basic` ( `ent_uid` varchar(100) DEFAULT NULL,`ent_code` varchar(100) DEFAULT NULL COMMENT '企业代码',`ent_category` tinyint(4) DEFAULT '1' COMMENT '企业类别:生产型,流通型',`row_id` bigint(20) NOT NULL AUTO_INCREMENT, `created_...
CREATE TABLE [ database_name . [ schema_name ] . | schema_name . ] table_name [ AS FileTable ] ( { <column_definition> | <computed_column_definition> | <column_set_definition> | [ <table_constraint> ] [ ,...n ] } )
SqlBasicCall表示一个基本的计算单元, 持有操作符和操作数, 如WHERE子句中的一个谓词表达式就会被解析为SqlBasicCall. SqlDdl是DDL语句解析结果的基类. 以CREATE TABLE语句为例, 它就会被解析成SqlCreateTable实例. 上文说到SqlCall其实是对SqlOperator的调用, 因此我们有必要进一步看一下SqlOperator的实现. SqlOperat...
simplify the process, U-SQL provides the ability to create a table from a U-SQL query expression. TheCREATE TABLE ASstatement will infer the schema from the query expression and will create a clustered table, thus the clustered index needs to be provided as part of theCREATE TABLE AS...
ORGANIZE BY HASH must not be specified if the table is using basic row format. If IN ACCELERATOR is specified, ORGANIZE BY HASH must not be specified. UNIQUE Specifies that DB2 enforces uniqueness of the hash key columns, preventing the table from containing two or more rows with the same ...
select DepartmentID as ‘部门名称’,COUNT(*) as ‘个数’ from BasicDepartment group by DepartmentID –这个就是使用了group by +字段 进行了分组,其中我们就可以理解为我们按照了部门的名称ID –DepartmentID将数据集进行了分组;然后再进行各个组的统计数据分别有多少; ...