PostgreSQL supports a TIMESTAMP data type that is used to store the DateTime values in the database. In PostgreSQL, “NULL” is used as the column’s default value, if no default value is explicitly declared. However, if a particular value is assigned as the column’s default value, ...
We didn’t specify the value for the “purchase_date” column. However, a default value will be assigned to the “purchase_date” column because of the “DEFAULT” keyword. Let’s run the “SELECT *” command to see the table’s data: The output authenticates the working of the DEFAULT...
FROM pg_catalog.pg_attrdef d WHERE d.adrelid = a.attrelid AND d.adnum = a.attnum AND a.atthasdef) ELSE '' END as column_default_value, CASE WHEN a.attnotnull = true THEN 'NOT NULL' ELSE 'NULL' END as column_not_null, a.attnum as attnum, e.max_attnum as max_attnum FR...
您可以命名特定对象以获取更多信息。使用+运算符还将列出表的约束和索引。postgres=# \d+ example_tbl Table "public.example_tbl"Column | Type | Collation | Nullable | Default | Storage | Compression | Stats target | Description---+---+---+---+---+---+---+---+---id | ...
hrdb=# COMMENTONCOLUMNtab_num.v5IS'大整型最小范围'; COMMENT hrdb=# COMMENTONCOLUMNtab_num.v6IS'大整型最大范围'; COMMENT hrdb=#--描述数据类型 hrdb=# \d+ tab_num Table"public.tab_num" Column| Type | Collation | Nullable |Default| Storage | Stats target | Description ...
alter table [表名] alter column [字段名] drop default; *修改表中的某行某列的数据: update [表名] set [目标字段名]=[目标值] where [该行特征]; *删除表中某行数据: delete from [表名] where [该行特征]; delete from [表名]; // 删空整个表 ...
NOT NULL constraint –ensure values in a column are not NULL. DEFAULT constraint –specify a default value for a column using the DEFAULT constraint. Section 14. PostgreSQL Data Types in Depth Boolean –store TRUE and FALSEvalues with the Boolean data type. CHAR, VARCHAR, and TEXT –learn ho...
Allow ALTER TABLE to add a column with a non-null default without doing a table rewrite (Andrew Dunstan, Serge Rielau) This is enabled when the default value is a constant.PostgreSQL 11版本的一些新特性PostgreSQL11: 新增三个默认角色 PostgreSQL11: 可通过GRNAT权限下放的四个系统函数 PostgreSQL...
default_expr:如果参数没有被指定值时要用作默认值的表达式 rettype:返回的数据类型,如果该函数不会返回一个值,可以指定返回类型为void。(后面详细讲) column_name:RETURNS TABLE语法中一个输出列的名称 culumn_type:RETURNS TABLE语法中的输出列的数据类型 ...
例:create table postgtest (id serial primary key,title varchar(255) not null, content text check(length(content) > 3),is_draft boolean default true , create_date timestamp default 'now'); 插入 INSERT INTO TABLE_NAME (column1, column2, column3,...columnN)VALUES (value1, value2, value...