Question

我有一个带有id列的DB2表，它有一个自动增量，这里是代码：

"id" BIGINT GENERATED BY DEFAULT AS IDENTITY(START WITH 1)

我手动插入已经有id值且不以1开头的值。现在当我向这个表添加记录时，它从1开始。我想在我的记录结束时开始。即，说最新记录有id 23，我希望新记录的id = 24。

我能用最少的努力在所有桌面上做到这一点吗？

Answer 1

您可以使用

db2 alter table <table_name> alter column <column_name> drop identity

和

db2 alter table <table_name> alter column <column_name> set generated always as identity (start with <max(column_identity_name)>)

-

user@host:/home/db2inst1:>db2 "CREATE TABLE TEST (ID BIGINT GENERATED BY DEFAULT AS IDENTITY(START WITH 1),    NAME CHAR(6))"

insert into test (NAME) VALUES ('test1')"
insert into test (NAME) VALUES ('test2')"
insert into test (NAME) VALUES ('test3')"
insert into test (NAME) VALUES ('test4')"
insert into test (NAME) VALUES ('test5')"
insert into test (NAME) VALUES ('test6')"
insert into test (NAME) VALUES ('test7')"
insert into test (ID,NAME) VALUES (4,'test8')"
insert into test (ID,NAME) VALUES (4,'test9')"
insert into test (ID,NAME) VALUES (4,'test10')"
insert into test (ID,NAME) VALUES (4,'test11')"
insert into test (ID,NAME) VALUES (4,'test12')"
insert into test (ID,NAME) VALUES (2,'test13')"
insert into test (ID,NAME) VALUES (2,'test14')"
insert into test (ID,NAME) VALUES (2,'test15')"
insert into test (ID,NAME) VALUES (3,'test16')"
insert into test (NAME) VALUES ('test17')"
insert into test (NAME) VALUES ('test18')"
insert into test (NAME) VALUES ('test19')"
insert into test (NAME) VALUES ('test20')"
insert into test (NAME) VALUES ('test21')"
insert into test (NAME) VALUES ('test22')"
insert into test (NAME) VALUES ('test23')"
insert into test (NAME) VALUES ('test24')"

-

user@host:/home/db2inst1:>db2 "select row_number() over (order by ID) as ROWID,ID,NAME from test"


                ID                   NAME  
-------------------- -------------------- ------
                   1                    1 test1 
                   2                    2 test2 
                   3                    2 test13
                   4                    2 test14
                   5                    2 test15
                   6                    3 test3 
                   7                    3 test16
                   8                    4 test4 
                   9                    4 test8 
                  10                    4 test9 
                  11                    4 test10
                  12                    4 test11
                  13                    4 test12
                  14                    5 test5 
                  15                    6 test6 
                  16                    7 test7 
                  17                    8 test17
                  18                    9 test18
                  19                   10 test19
                  20                   11 test20
                  21                   12 test21
                  22                   13 test22
                  23                   14 test23
                  24                   15 test24

  24 record(s) selected.

user@host:/home/db2inst1:>db2 alter table test alter column id drop identity
DB20000I  The SQL command completed successfully.

我从max row_number找到起始值;

user@host:/home/db2inst1:>db2 "alter table test alter column id set generated always as identity (start with 25)"
DB20000I  The SQL command completed successfully.
insert into test (NAME) VALUES ('test25')"
DB20000I  The SQL command completed successfully.
user@host:/home/db2inst1:>db2 "select row_number() over (order by ID) as ROWID,ID,NAME from test"

ROWID                ID                   NAME  
-------------------- -------------------- ------
                   1                    1 test1 
                   2                    2 test2 
                   3                    2 test13
                   4                    2 test14
                   5                    2 test15
                   6                    3 test3 
                   7                    3 test16
                   8                    4 test4 
                   9                    4 test8 
                  10                    4 test9 
                  11                    4 test10
                  12                    4 test11
                  13                    4 test12
                  14                    5 test5 
                  15                    6 test6 
                  16                    7 test7 
                  17                    8 test17
                  18                    9 test18
                  19                   10 test19
                  20                   11 test20
                  21                   12 test21
                  22                   13 test22
                  23                   14 test23
                  24                   15 test24
                  25                   25 test25

  25 record(s) selected.

Answer 2

基于@mustaccio评论，最直接的目标是：

ALTER TABLE "tableName" ALTER COLUMN "columnName" RESTART WITH <new index value>

如何使IDENTITY`id`列以不同的值开头？

2 个答案: