CREATE SERVER _server_name_ [ TYPE '_server_type_' ] [ VERSION '_server_version_' ] FOREIGN DATA WRAPPER _fdw_name_ [ OPTIONS ( _option_ '_value_' [, ... ] ) ]CREATE SEQUENCE定义一个新序列发生器。CREATE [ TEMPORARY | TEMP ] SEQUENCE name [ INCREMENT [ BY ] increment ] [ ...
ALTER SEQUENCE 修改一个序列生成器的定义。 ALTERSEQUENCEname[INCREMENT[BY]increment][MINVALUEminvalue|NOMINVALUE][MAXVALUEmaxvalue|NOMAXVALUE][RESTART[WITH]start][CACHEcache][[NO]CYCLE] 复制 ALTER TABLE 修改表的定义。 ALTERTABLE[ONLY]name[*]action[,...]ALTERTABLE[ONLY]name[*]RENAME[COLUMN]col...
Note: Here nextval() function is used to get the next value instead of the standard's NEXT VALUE FOR expression. Let use this sequence in an INSERT command: Now use the above sequence in an INSERT command : Sample table 'test': Output: postgres=# SELECT * FROM test; id | sname | r...
1postgres=#createsequence seq_tb1 incrementby1minvalue1maxvalue100000000startwith1no cycle ;2CREATESEQUENCE3postgres=#createsequence seq_tb2 incrementby1minvalue100000001maxvalue200000000startwith100000001no cycle ;4CREATESEQUENCE5postgres=#createsequence seq_tb3 incrementby1minvalue200000001maxvalue300000000...
COALESCE(value[, ...]) 和CASE表达式一样,COALESCE将不会计算不需要用来判断结果的参数。也就是说,在第一个非空参数右边的参数不会被计算。 3. NULLIF: 当且仅当value1和value2相等时,NULLIF才返回NULL。否则它返回value1。 NULLIF(value1, value2) MyTest=> SELECT NULLIF('abc','abc'); nullif ---...
创建一个序列 create sequence seq_test start with 1 increment by 1 no minvalue no maxvalue cache 1; 将表的字段默认值设置为该序列的next值 create table tb_test(a int not null default nextval('seq_test')); 如果向表中插入记录时字段a没有被指定,则seq_test表读取序列的下一个值作为a的值 直...
-- Check the current value of the sequence SELECT currval('employees_emp_id_seq'); Explanation: nextval:Retrieves the next sequence value. setval:Manually sets the sequence value. currval:Returns the current value of the sequence (only within the same session). ...
Open the sequence - the Last value is empty. Verify sequence value via sql: select currval('testtable_id_seq') => 1 - current value is not changed (that's ok - we really set next value) Insert any data and watch the created id: insert into testtable(testchar) values ('test');...
CREATE SEQUENCE 定义一个新序列发生器。 CREATE [ TEMPORARY | TEMP ] SEQUENCE name [ INCREMENT [ BY ] increment ] [ MINVALUE minvalue | NO MINVALUE ] [ MAXVALUE maxvalue | NO MAXVALUE ] [ START [ WITH ] start ] [ CACHE cache ] [ [ NO ] CYCLE ] ...
首先打开 relation即VM文件,随后执行check_relation_relkind函数,此处只支持RELKIND_RELATION、RELKIND_INDEX、RELKIND_MATVIEW、RELKIND_SEQUENCE、RELKIND_TOASTVALUE几种类型。 再通过pg_visibility_tupdesc组装出tup的描述 。一般情况下,tupdesc能够直接在系统表里获取。而此处由于数据格式固定,因此需要自行生成 。