Sql 如何在一个表中选择另一个表中值不为null的列

我有两个SQL表（我使用的是SQLite）

如何获取表2中至少有一行代码table1不为null的所有table1内容

select
  a.*
from 
 Table1 a
where
  exists (select * from Table2 b where b.codeTable1 is not null)

或

不确定您的查询的确切目的

或

---

不确定查询的确切目的。

我想您需要一个相关的子查询：

select t1.*
from Table1 t1
where exists (select 1
              from Table2 t2
              where t2.code = t1.code and t2.codeTable1 is not null
             );

---

这似乎是对您的需求的非常直接的翻译。

我认为您需要一个相关的子查询：

select t1.*
from Table1 t1
where exists (select 1
              from Table2 t2
              where t2.code = t1.code and t2.codeTable1 is not null
             );

---

这似乎是对您的需求的非常直接的翻译。

一个简单的连接应该可以做到：

问题是：

select 
    *
from
    table1
    join table2 on table1.code = table2.table1_code
where
    table1.code is not null

以下是完整的示例：

use example;

drop table if exists table1;
drop table if exists table2;

create table table1 (
    code varchar(64)
);

create table table2 (
    code varchar(64),
    table1_code varchar(64) references table1(code)
);

insert into table1 values('CODE1');
insert into table1 values('CODE2');
insert into table1 values('CODE3');
insert into table1 values('CODE4');
insert into table1 values('CODE5');
insert into table1 values(null);


insert into table2 values('VAL1', 'CODE1');
insert into table2 values('VAL3', 'CODE3');
insert into table2 values('VAL5', 'CODE5');
insert into table2 values(null, null);
insert into table2 values(null, null);
insert into table2 values(null, null);

select 
    *
from
    table1
    join table2 on table1.code = table2.table1_code
where
    table1.code is not null

+ --------- + --------- + ---------------- +
| code      | code      | table1_code      |
+ --------- + --------- + ---------------- +
| CODE1     | VAL1      | CODE1            |
| CODE3     | VAL3      | CODE3            |
| CODE5     | VAL5      | CODE5            |
+ --------- + --------- + ---------------- +
3 rows

---

一个简单的连接应该可以做到这一点：

问题是：

select 
    *
from
    table1
    join table2 on table1.code = table2.table1_code
where
    table1.code is not null

以下是完整的示例：

use example;

drop table if exists table1;
drop table if exists table2;

create table table1 (
    code varchar(64)
);

create table table2 (
    code varchar(64),
    table1_code varchar(64) references table1(code)
);

insert into table1 values('CODE1');
insert into table1 values('CODE2');
insert into table1 values('CODE3');
insert into table1 values('CODE4');
insert into table1 values('CODE5');
insert into table1 values(null);


insert into table2 values('VAL1', 'CODE1');
insert into table2 values('VAL3', 'CODE3');
insert into table2 values('VAL5', 'CODE5');
insert into table2 values(null, null);
insert into table2 values(null, null);
insert into table2 values(null, null);

select 
    *
from
    table1
    join table2 on table1.code = table2.table1_code
where
    table1.code is not null

+ --------- + --------- + ---------------- +
| code      | code      | table1_code      |
+ --------- + --------- + ---------------- +
| CODE1     | VAL1      | CODE1            |
| CODE3     | VAL3      | CODE3            |
| CODE5     | VAL5      | CODE5            |
+ --------- + --------- + ---------------- +
3 rows