Question

在sqlite中，如何在另一个表/视图列中将列的值限制为不？

例如

sqlite> create table tab1(col1 check (col1 not in (1,2)));

做我想要的，除了它似乎只是排除硬编码值。但是，以下操作无效 -

sqlite> create table tab2(vals_to_exclude);
sqlite> insert into tab2 values(1);
sqlite> insert into tab2 values(2);
sqlite> create table tab3(col1 check (col1 not in (select vals_to_exclude from tab2)));
Error: subqueries prohibited in CHECK constraints

是否可以约束列以排除动态确定的值集？

Answer 1

如果内置机制不足，请使用trigger：

手动执行检查

CREATE TRIGGER tab3_col1_not_in_tab2
BEFORE INSERT ON tab3   -- you also need a trigger for UPDATEs
FOR EACH ROW
WHEN EXISTS (SELECT 1
             FROM tab2
             WHERE vals_to_exclude = NEW.col1)
BEGIN
    SELECT RAISE(FAIL, "col1 conflicts with tab2");
END;

或者，或者：

CREATE TRIGGER tab3_col1_not_in_tab2
BEFORE INSERT ON tab3   -- you also need a trigger for UPDATEs
FOR EACH ROW
BEGIN
    SELECT RAISE(FAIL, "col1 conflicts with tab2")
    FROM tab2
    WHERE vals_to_exclude = NEW.col1;
END;

sqlite列约束不在值集中

1 个答案: