Variables 会话变量作为标识符

在Snowflake中使用会话变量作为标识符时遇到了一些问题。我已经审阅了文件：

我能够让他们的例子发挥作用，但在我看来，所提出的概念的逻辑应用不起作用。下面是一个有效的示例（首先将数据库和模式设置为沙盒）：

输入：

set (table_n, column_n) = ('test', 'c1');
select $table_n, $column_n;

create or replace table identifier($table_n) (c1 number);
insert into identifier($table_n) (c1) values (1), (2), (3);
select identifier($column_n) from identifier($table_n);

insert into identifier($table_n) (identifier($column_n)) values (5), (6), (7);

create or replace table identifier($table_n) (identifier($column_n) number);

set (table_n, column_n) = ('test', '\'c1\'');
select $table_n, $column_n;

create or replace table identifier($table_n) ("'c1'" number);
insert into identifier($table_n) ("'c1'") values (1), (2), (3);

select identifier($column_n) from identifier($table_n);

输出：

$TABLE_N    $COLUMN_N
test        c1

c1
1
2
3

SQL compilation error: syntax error line 1 at position 44 unexpected '('. syntax error line 1 at position 45 unexpected '$column_n'. syntax error line 1 at position 55 unexpected ')'.

SQL compilation error: syntax error line 1 at position 56 unexpected '('. syntax error line 1 at position 74 unexpected ')'.

$TABLE_N    $COLUMN_N
test        'c1'

number of rows inserted
3

SQL compilation error: error line 1 at position 18 invalid identifier '$column_n'

输入：

set (table_n, column_n) = ('test', 'c1');
select $table_n, $column_n;

create or replace table identifier($table_n) (c1 number);
insert into identifier($table_n) (c1) values (1), (2), (3);
select identifier($column_n) from identifier($table_n);

insert into identifier($table_n) (identifier($column_n)) values (5), (6), (7);

create or replace table identifier($table_n) (identifier($column_n) number);

set (table_n, column_n) = ('test', '\'c1\'');
select $table_n, $column_n;

create or replace table identifier($table_n) ("'c1'" number);
insert into identifier($table_n) ("'c1'") values (1), (2), (3);

select identifier($column_n) from identifier($table_n);

输出：

$TABLE_N    $COLUMN_N
test        c1

c1
1
2
3

SQL compilation error: syntax error line 1 at position 44 unexpected '('. syntax error line 1 at position 45 unexpected '$column_n'. syntax error line 1 at position 55 unexpected ')'.

SQL compilation error: syntax error line 1 at position 56 unexpected '('. syntax error line 1 at position 74 unexpected ')'.

$TABLE_N    $COLUMN_N
test        'c1'

number of rows inserted
3

SQL compilation error: error line 1 at position 18 invalid identifier '$column_n'

到目前为止还不错。这些都是从文件中提出来的。但是，当我尝试在稍微不同的上下文中使用标识符时，操作失败，并显示一条无用的错误消息

输入：

set (table_n, column_n) = ('test', 'c1');
select $table_n, $column_n;

create or replace table identifier($table_n) (c1 number);
insert into identifier($table_n) (c1) values (1), (2), (3);
select identifier($column_n) from identifier($table_n);

insert into identifier($table_n) (identifier($column_n)) values (5), (6), (7);

create or replace table identifier($table_n) (identifier($column_n) number);

set (table_n, column_n) = ('test', '\'c1\'');
select $table_n, $column_n;

create or replace table identifier($table_n) ("'c1'" number);
insert into identifier($table_n) ("'c1'") values (1), (2), (3);

select identifier($column_n) from identifier($table_n);

输出：

$TABLE_N    $COLUMN_N
test        c1

c1
1
2
3

SQL compilation error: syntax error line 1 at position 44 unexpected '('. syntax error line 1 at position 45 unexpected '$column_n'. syntax error line 1 at position 55 unexpected ')'.

SQL compilation error: syntax error line 1 at position 56 unexpected '('. syntax error line 1 at position 74 unexpected ')'.

$TABLE_N    $COLUMN_N
test        'c1'

number of rows inserted
3

SQL compilation error: error line 1 at position 18 invalid identifier '$column_n'

输入：

set (table_n, column_n) = ('test', 'c1');
select $table_n, $column_n;

create or replace table identifier($table_n) (c1 number);
insert into identifier($table_n) (c1) values (1), (2), (3);
select identifier($column_n) from identifier($table_n);

insert into identifier($table_n) (identifier($column_n)) values (5), (6), (7);

create or replace table identifier($table_n) (identifier($column_n) number);

set (table_n, column_n) = ('test', '\'c1\'');
select $table_n, $column_n;

create or replace table identifier($table_n) ("'c1'" number);
insert into identifier($table_n) ("'c1'") values (1), (2), (3);

select identifier($column_n) from identifier($table_n);

输出：

$TABLE_N    $COLUMN_N
test        c1

c1
1
2
3

SQL compilation error: syntax error line 1 at position 44 unexpected '('. syntax error line 1 at position 45 unexpected '$column_n'. syntax error line 1 at position 55 unexpected ')'.

SQL compilation error: syntax error line 1 at position 56 unexpected '('. syntax error line 1 at position 74 unexpected ')'.

$TABLE_N    $COLUMN_N
test        'c1'

number of rows inserted
3

SQL compilation error: error line 1 at position 18 invalid identifier '$column_n'

当标识符的开头或结尾有一个引号时，我也会出错。如果我们返回到第一个有效的示例，只需将列名更改为“'c1'”，它就会失败

输入：

set (table_n, column_n) = ('test', 'c1');
select $table_n, $column_n;

create or replace table identifier($table_n) (c1 number);
insert into identifier($table_n) (c1) values (1), (2), (3);
select identifier($column_n) from identifier($table_n);

insert into identifier($table_n) (identifier($column_n)) values (5), (6), (7);

create or replace table identifier($table_n) (identifier($column_n) number);

set (table_n, column_n) = ('test', '\'c1\'');
select $table_n, $column_n;

create or replace table identifier($table_n) ("'c1'" number);
insert into identifier($table_n) ("'c1'") values (1), (2), (3);

select identifier($column_n) from identifier($table_n);

输出：

$TABLE_N    $COLUMN_N
test        c1

c1
1
2
3

SQL compilation error: syntax error line 1 at position 44 unexpected '('. syntax error line 1 at position 45 unexpected '$column_n'. syntax error line 1 at position 55 unexpected ')'.

SQL compilation error: syntax error line 1 at position 56 unexpected '('. syntax error line 1 at position 74 unexpected ')'.

$TABLE_N    $COLUMN_N
test        'c1'

number of rows inserted
3

SQL compilation error: error line 1 at position 18 invalid identifier '$column_n'

输入：

set (table_n, column_n) = ('test', 'c1');
select $table_n, $column_n;

create or replace table identifier($table_n) (c1 number);
insert into identifier($table_n) (c1) values (1), (2), (3);
select identifier($column_n) from identifier($table_n);

insert into identifier($table_n) (identifier($column_n)) values (5), (6), (7);

create or replace table identifier($table_n) (identifier($column_n) number);

set (table_n, column_n) = ('test', '\'c1\'');
select $table_n, $column_n;

create or replace table identifier($table_n) ("'c1'" number);
insert into identifier($table_n) ("'c1'") values (1), (2), (3);

select identifier($column_n) from identifier($table_n);

输出：

$TABLE_N    $COLUMN_N
test        c1

c1
1
2
3

SQL compilation error: syntax error line 1 at position 44 unexpected '('. syntax error line 1 at position 45 unexpected '$column_n'. syntax error line 1 at position 55 unexpected ')'.

SQL compilation error: syntax error line 1 at position 56 unexpected '('. syntax error line 1 at position 74 unexpected ')'.

$TABLE_N    $COLUMN_N
test        'c1'

number of rows inserted
3

SQL compilation error: error line 1 at position 18 invalid identifier '$column_n'

输入：

set (table_n, column_n) = ('test', 'c1');
select $table_n, $column_n;

create or replace table identifier($table_n) (c1 number);
insert into identifier($table_n) (c1) values (1), (2), (3);
select identifier($column_n) from identifier($table_n);

insert into identifier($table_n) (identifier($column_n)) values (5), (6), (7);

create or replace table identifier($table_n) (identifier($column_n) number);

set (table_n, column_n) = ('test', '\'c1\'');
select $table_n, $column_n;

create or replace table identifier($table_n) ("'c1'" number);
insert into identifier($table_n) ("'c1'") values (1), (2), (3);

select identifier($column_n) from identifier($table_n);

输出：

$TABLE_N    $COLUMN_N
test        c1

c1
1
2
3

SQL compilation error: syntax error line 1 at position 44 unexpected '('. syntax error line 1 at position 45 unexpected '$column_n'. syntax error line 1 at position 55 unexpected ')'.

SQL compilation error: syntax error line 1 at position 56 unexpected '('. syntax error line 1 at position 74 unexpected ')'.

$TABLE_N    $COLUMN_N
test        'c1'

number of rows inserted
3

SQL compilation error: error line 1 at position 18 invalid identifier '$column_n'

---

非常感谢您的帮助。我真的很想了解幕后发生了什么，所以我真的知道如何使用雪花。谢谢大家!

对于您的第一个SQL错误，我能够使用下面的语句将值插入表中，而不必指定列（在本例中为c1）：

INSERT INTO identifier($table_n)  VALUES (5), (6), (7);

这似乎是因为C1默认为数字索引：其中选择输出为：

但是对于 创建或替换标识符（变量）标识符（变量）。。。； 似乎引起了一些问题。 Select语句中用逗号分隔的两个变量不会引发错误

我确实找到了SQL标识符的注释：

标识符（数据库名、表名、列名等）不能 以特殊字符开头，除非整个名称包含在 双引号。有关更多信息，请参阅对象标识符

起草结论：（variable variable）只能在会话变量中执行，不能在SQL变量中执行（例如在JDBCAPI中）

想法

增加： 此外，当我将最后一个select语句更改为时，它没有给出预期的结果

select $column_n from identifier($table_n);

---

是列“$column\n”的名称还是变量名？这是变量名。变量是通过以下方式创建的：``set variable\u name=value```然后它们被引用：``选择$variable\u name``对于第一个错误，我想您可以使用它作为一种简单的解决方法，只需为不使用的列指定空值或默认值，但它似乎仍然被破坏了。尽管如此，它还是完成了任务，所以谢谢你的想法。我不明白你的意思“（变量）只能在会话变量中执行，不能在SQL变量中执行”，你能详细说明一下吗？运行上一个select语句时发生了什么？