> create table t_user(id int(10) ,name varchar(32) not null,email varchar(128)); 15.2唯一性约束(unique) 作用:unique约束的字段具有唯一性,不可重复,但是可以为空(null)。 案例:修改之前的t_user表结构,把email设置为唯一性 > alter table t_user modify email varchar(128) unique; 15.3组合使用 ...
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...
It has a "constraint_specification" for the Create table statement for primary_keyt etc. I tried but couldn't find the "constraint_specification" in Cloudera site for Hive. My questions are 1. Is it possible to create a Hive table with Not Null constraints? If yes, can you please provid...
SQL命令 CREATE TABLE(三) 字段数据约束 数据约束控制字段允许使用的值、字段的默认值以及数据值使用的排序规则类型。所有这些数据约束都是可选的。可以按任何顺序指定多个数据约束,并以空格分隔。 NULL和NOT NULL NOT NULL数据约束关键字指定该字段不接受空值;换句话说,每条记录都必须为该字段指定一个值。NULL和空字...
Create a table with check constraint : Check « Table « Oracle PL/SQL TutorialOracle PL/SQL Tutorial Table Check SQL> SQL> create table employees 2 ( empno NUMBER(4) constraint E_PK 3 primary key 4 constraint E_EMPNO_CHK 5 check (empno > 7000)) ; Table created. SQL> SQL> drop...
= column_set_name XML COLUMN_SET FOR ALL_SPARSE_COLUMNS <table_constraint> ::= [ CONSTRAINT constraint_name ] { { PRIMARY KEY | UNIQUE } [ CLUSTERED | NONCLUSTERED ] ( column_name [ ASC | DESC ] [ ,... n ] ) [ WITH FILLFACTOR = fillfactor | WITH ( <index_option> [ ,... ...
第十六章 SQL命令 CREATE TABLE(三) 字段数据约束 数据约束控制字段允许使用的值、字段的默认值以及数据值使用的排序规则类型。所有这些数据约束都是可选的。可以按任何顺序指定多个数据约束,并以空格分隔。 NULL和NOT NULL NOT NULL数据约束关键字指定该字段不接受空值;换句话说,每条记录都必须为该字段指定一个值。
= column_set_name XML COLUMN_SET FOR ALL_SPARSE_COLUMNS <table_constraint> ::= [ CONSTRAINT constraint_name ] { { PRIMARY KEY | UNIQUE } [ CLUSTERED | NONCLUSTERED ] ( column_name [ ASC | DESC ] [ ,... n ] ) [ WITH FILLFACTOR = fillfactor | WITH ( <index_option> [ ,... ...
] 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 ...
{ TEMPORARY | TEMP } | UNLOGGED ] TABLE [ IF NOT EXISTS ] table_name OF type_name [ ( { column_name [ WITH OPTIONS ] [ column_constraint [ ... ] ] | table_constraint } [, ... ] ) ] [ PARTITION BY { RANGE | LIST | HASH } ( { column_name | ( expression ) } [ ...