Write a SQL query to create a table with three columns: id, name, and age. Add a primary key constraint on the id column. Write a SQL query to create a table with four columns: product_id, product_name, price, and quantity. Ensure that the price column cannot have negative values...
MySQL常见的建表约束(Create Table Constraints) 一、MySQL约束类型 约束名称 描述 NOT NULL 非空约束 UNIQUE 唯一约束,取值不允许重复, PRIMARY KEY 主键约束(主关键字),自带非空、唯一、索引 FOREIGN KEY 外键约束(外关键字)
可以在创建表时规定约束(通过 CREATE TABLE 语句),或者在表创建之后也可以(通过 ALTER TABLE 语句)。 我们将主要探讨以下几种约束: NOT NULL UNIQUE PRIMARY KEY FOREIGN KEY CHECK DEFAULT SQL NOT NULL 约束 NOT NULL 约束强制列不接受 NULL 值。 SQL UNIQUE 约束 SQL UNIQUE 约束 UNIQUE 约束唯一标识数据库表...
] referenced_table_name [ ( ref_column ) ] | CHECK ( logical_expression ) } <table_constraint> ::= [ CONSTRAINT constraint_name ] { { PRIMARY KEY | UNIQUE } { NONCLUSTERED ( column_name [ ASC | DESC ] [ ,... n ]) | NONCLUSTERED HASH ( column_name [ ,... n ] ) WITH ...
When creating a managed U-SQL table with a schema, a table schema has to be provided that contains at least one table column definition. Syntax Create_Managed_Table_With_Schema_Statement := 'CREATE' 'TABLE' ['IF' 'NOT' 'EXISTS']IdentifierTable_With_Schema. ...
CREATE TABLE [IF NOT EXISTS] table_name( column_definition1, column_definition2, …….., table_constraints ); 也可简写为: CREATE TABLE table_name (column_name column_type); 上述语法的参数说明如下: 以下例子中我们将在 RUNOON 数据库中创建数据...
CREATE TABLE (Transact-SQL) 在SQL Server 2008 R2 中创建新表。 Transact-SQL 语法约定 语法 CREATE TABLE [ database_name . [ schema_name ] . | schema_name . ] table_name ( { <column_definition> | <computed_column_definition> | <column_set_definition> | [ <table_constraint> ] [ ,....
We can also add different types of constraints while creating a table. For example, CREATETABLECompanies (idintNOTNULL,namevarchar(50)NOTNULL, addresstext, emailvarchar(50)NOTNULL, phonevarchar(10) ); Here, the constraintNOT NULLis added to the columnsid,nameandemail. It simply means, these...
1. Is it possible to create a Hive table with Not Null constraints? If yes, can you please provide me syntax. 2. What are the constraints are supported in Hive table? If possible please provide me the link which has the details on constraints supported by Hive for Cloudera distribution. ...
LIKE source_table [ like_option … ] The LIKE clause specifies a table from which the new table automatically copies all column names, their data types, and their not-null constraints. 如上所示,当使用LIKE子句做表复制时,默认会自动拷贝所有字段、字段类型以及它们的NOT-NULL约束,这也就解释了刚才为...