如何在sqlite中为字段分配空值

Question

我想为SQLite中的字段分配null ，但与此无关：

update t set n=null where n=0;

Answer 1

I can not reproduce your problem. From what you write, I guess your table looks like this:

CREATE TABLE t (n integer);

Inserting data:

insert into t values (1);
insert into t values (2);
insert into t values (3);
insert into t values (0);

Updating the data with your UPDATE :

update t set n = null where n = 0;

Now the table looks like this:

sqlite> .dump
PRAGMA foreign_keys=OFF;
BEGIN TRANSACTION;
CREATE TABLE t (n integer);
INSERT INTO "t" VALUES(1);
INSERT INTO "t" VALUES(2);
INSERT INTO "t" VALUES(3);
INSERT INTO "t" VALUES(NULL);
COMMIT;

There might be no output after the UPDATE but it has the desired effect.