如何执行多个独特集（列组合）是相互排斥的SQLite中？

Question

考虑含ABC为空的列，DEF和XYZ表。如何强制应用经过：

1. 组1（“ABC”）是独一无二的，如果“ABC”不为空，并
2. 集2（“闪避，XYZ”）是独一无二的，如果既有“变形点焊”和“XYZ”不为空，并且
3. 上述集只有一个是有效的（包含非空值）。

这是我曾尝试代码：

--# sqlite3 --version 
-- 3.13.0 .... 

DROP TABLE IF EXISTS try; 
CREATE TABLE try(
    -- 'abc' should be null,     when 'def' and 'xyz' are not null. 
    -- 'abc' should be not be null,   when 'def' and 'xyz' are null. 
    -- 'def' and 'xyz' should be null,  when 'abc' is not null. 
    -- 'def' and 'xyz' should be not be null, when 'abc' is null. 

    abc TEXT, 
    def TEXT, 
    xyz TEXT, 
    CONSTRAINT combo_1 UNIQUE(abc), 
    CONSTRAINT combo_2 UNIQUE(def, xyz) 
); 

INSERT into try(abc)   VALUES("a1");    -- should succeed 
INSERT into try(def, xyz)  VALUES("d2", "x2");  -- should succeed 
-- 
INSERT into try(abc)   VALUES(null);    -- should not be allowed 
INSERT into try(abc, def)  VALUES("a4", "d4");  -- should not be allowed 
INSERT into try(abc, xyz)  VALUES("a5", "x5");  -- should not be allowed 
INSERT into try(abc, def, xyz) VALUES("a6", "d6", "x6"); -- should not be allowed 
-- 
INSERT into try(def)   VALUES(null);    -- should not be allowed 
INSERT into try(def)   VALUES("d8");    -- should not be allowed 
-- 
INSERT into try(xyz)   VALUES(null);    -- should not be allowed 
INSERT into try(xyz)   VALUES("x10");    -- should not be allowed 
-- 
INSERT into try(def, xyz)  VALUES(null, null);  -- should not be allowed 
INSERT into try(def, xyz)  VALUES("d12", null);  -- should not be allowed 
INSERT into try(def, xyz)  VALUES(null, "x13");  -- should not be allowed 

INSERT into try(abc, def, xyz) VALUES(null, null, null); -- should not be allowed 

.headers ON 
select rowid,* from try; 

.echo on 
-- 
-- Only these 2 rows should be present: 
-- 1|a1|| 
-- 2||d2|x2 
-- 

但是，所有的14个刀片成功，当我想只有第2成功。

Answer 1

换句话说：abc和def列的NULL值应该不同，而def和xyz列的NULL值应该是相同的。

CHECK((abc IS NULL) <> (def IS NULL)), 
CHECK((def IS NULL) = (xyz IS NULL))