我有一个名为student的表,id和name作为PostgreSQL中的字段:
Create table student (id int, name text[]);
我需要为name字段添加约束.这意味着它必须只接受该字段的字符.但字段名称是文本数组.
我试过这个检查约束:
Alter table student
add constraint stud_const check (ALL(name) NOT LIKE '%[^a-zA-Z]%');
但它抛出了这个错误:
ERROR: syntax error atERROR: syntax error at or near "all"
LINE 1: ... student add constraint stud_const check (all(name) ...
or near "all"
我怎么能解决这个问题?约束应设置为整个数组.
最佳答案 有必要将
unnest
数组与
regular expression
匹配:
select bool_and (n ~ '^[a-zA-Z]*$')
from unnest(array['John','Mary']) a(n)
;
bool_and
----------
t
bool_and
.由于在检查约束中不可能使用子查询将其包装在函数中:
create function check_text_array_regex (
a text[], regex text
) returns boolean as $$
select bool_and (n ~ regex)
from unnest(a) s(n);
$$language sql immutable;
并使用检查约束中的函数:
create table student (
id serial,
name text[] check (check_text_array_regex (name, '^[a-zA-Z]*$'))
);
测试一下:
insert into student (name) values (array['John', 'Mary']);
INSERT 0 1
insert into student (name) values (array['John', 'Mary2']);
ERROR: new row for relation "student" violates check constraint "student_name_check"
DETAIL: Failing row contains (2, {John,Mary2}).