SEQUENCES

显示有关序列的信息。

示例

创建简单的序列：

=> CREATE SEQUENCE my_seq MAXVALUE 5000 START 150;
CREATE SEQUENCE

返回有关刚创建的序列的信息：

=> \x
Expanded display is on.
=> SELECT * FROM sequences;
-[ RECORD 1 ]-------+------------------
sequence_schema     | public
sequence_name       | my_seq
owner_name          | dbadmin
identity_table_name |
session_cache_count | 250000
allow_cycle         | f
output_ordered      | f
increment_by        | 1
minimum             | 1
maximum             | 5000
current_value       | 149
sequence_schema_id  | 45035996273704966
sequence_id         | 45035996273844996
owner_id            | 45035996273704962
identity_table_id   | 0

标识列是仅适用于数字列类型的序列。要识别表中的列（如有）是标识列，请搜索 COLUMNS 表以查找表中的标识列：

=> CREATE TABLE testid (c1 IDENTITY(1, 1, 1000), c2 INT);
=> \x
Expanded display is on.
=> SELECT * FROM COLUMNS WHERE is_identity='t' AND table_name='testid';
-[ RECORD 1 ]------------+------------------
table_id                 | 45035996274150730
table_schema             | public
table_name               | testid
is_system_table          | f
column_name              | c1
data_type                | int
data_type_id             | 6
data_type_length         | 8
character_maximum_length |
numeric_precision        |
numeric_scale            |
datetime_precision       |
interval_precision       |
ordinal_position         | 1
is_nullable              | f
column_default           |
is_identity              | t

使用 SEQUENCES 表获得关于 testid 中序列的详细信息：

=> SELECT * FROM sequences WHERE identity_table_name='testid';
-[ RECORD 1 ]-------+--------------------
sequence_schema     | public
sequence_name       | testid_c1_seq
owner_name          | dbadmin
identity_table_name | testid
session_cache_count | 1000
allow_cycle         | f
output_ordered      | f
increment_by        | 1
minimum             | 1
maximum             | 9223372036854775807
current_value       | 0
sequence_schema_id  | 45035996273704976
sequence_id         | 45035996274150770
owner_id            | 45035996273704962
identity_table_id   | 45035996274150768

使用 vsql 命令 \ds 以返回序列的列表。以下结果显示了先前示例中创建的两个序列。如果存在更多序列，表会将其列出。

新序列的 CurrentValue 比您在 CREATE SEQUENCE 和 IDENTITY 命令中指定的起始编号少 1，因为您还未使用 NEXTVAL 实例化序列来分配其缓存或提供其首批初始值。

=> \ds
 List of Sequences
-[ RECORD 1 ]+--------------------
Schema       | public
Sequence     | my_seq
CurrentValue | 149
IncrementBy  | 1
Minimum      | 1
Maximum      | 5000
AllowCycle   | f
Comment      |
-[ RECORD 2 ]+--------------------
Schema       | public
Sequence     | testid_c1_seq
CurrentValue | 0
IncrementBy  | 1
Minimum      | 1
Maximum      | 9223372036854775807
AllowCycle   | f
Comment      |