postgresql 如何将整数转换为串行
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How to convert integer to serial
提问by drnextgis
I have a table which has a primary key column "gid" and its type is "Integer NOT NULL". I want to convert it into "Serial NOT NULL" so that I can insert some values into this table. I used following commands to convert it into serial:
我有一个表，它有一个主键列“gid”，它的类型是“Integer NOT NULL”。我想将其转换为“Serial NOT NULL”，以便我可以在该表中插入一些值。我使用以下命令将其转换为串行：
CREATE SEQUENCE test_table_gid_seq
INCREMENT 1
MINVALUE 1
MAXVALUE 2147483648 START 1
CACHE 1;
ALTER TABLE test_table ALTER COLUMN gid
SET DEFAULT nextval('test_table_gid_seq'::regclass);
This command converted integer to serial. But while I entered some data to the table following error occurred:
此命令将整数转换为串行。但是当我向表中输入一些数据时，发生了以下错误：
ERROR: duplicate key value violates unique constraint "pk_test".
错误：重复的键值违反了唯一约束“pk_test”。
Please help me to solve this. Is there any other method to convert integer to serial?
请帮我解决这个问题。有没有其他方法可以将整数转换为串行？
回答by drnextgis
Select max value of gid column (max_gid):
选择 gid 列的最大值 (max_gid)：
SELECT max(gid) FROM test_table;
And use it as start point for sequence (probably, max_gid+1):
并将其用作序列的起点（可能是 max_gid+1）：
ALTER SEQUENCE test_table_gid_seq RESTART WITH max_gid;
