stuid number(8) primary key, stuname varchar2(30) not null, stuphone varcha2(11), classid number(2) references t_class(classid) [on delete set null/cascade]可以添加操作策略,默认no action ) insert into t_student values(
set_config(setting_name,new_value,is_local) text 设置参数并返回新值 current_setting用于以查询形式获取setting_name设置的当前数值。它和SQL命令SHOW是等效的。 比如: MyTest=# SELECT current_setting('datestyle'); current_setting --- ISO, YMD (1 row) set_config将参数setting_name设置为new_value...
ALTER TABLE flow DROP CONSTRAINT FlowPrimaryKey ; 1. 2. 3. 创建主键自增id CREATE SEQUENCE id_seq START WITH 1 INCREMENT BY 1 NO MINVALUE NO MAXVALUE CACHE 1; # 设置自增序列 alter table testtable alter column id set default nextval('id_seq'); # 赋予表自增 1. 2. 3. 4. 5. 6....
成功重置自增id 可以通过 SHOW TABLE STATUS WHERE NAME = 'user'; 查看表状态
UPDATE items SET counter = counter + 1 WHERE key = 'hello'; -- 一边阻塞 world,一边等着 hello END; 如果这些事务同时运行,它们很可能会互相卡住,永远无法完成。Postgres 会在一秒钟左右后识别出这种情况,并取消其中一个事务,让另一个事务完成。出现这种情况时,你应该检查一下自己的应用程序,看看能否让事务...
columnN datatype,PRIMARYKEY(oneormore columns ) ); 写法1: test=#createtablecompany(idintprimarykeynotnull, name textnotnull, ageintnotnull,addresschar(50) , salaryreal); 写法2: test=#CREATETABLECOMPANY( test(# IDINTPRIMARYKEYNOTNULL, ...
‘batch’ - Uses psycopg2.extras.execute_batch so that multiple copies of a SQL query, each one corresponding to a parameter set passed to executemany(), are joined into a single SQL string separated by a semicolon. This is the same behavior as was provided by the use_batch_mode=True fl...
PRIMARY KEY此约束是UNIQUE和NOT NULL约束相结合,确保列没有条目为NULL,并且每个条目都不同。 FOREIGN KEYFOREIGN KEY是一个表中的一列,它引用另一个表的PRIMARY KEY。此约束用于将两个表链接在一起:FOREIGN KEY列的条目必须已经存在于父PRIMARY KEY列中,写入过程才算成功。
); ps.setTimestamp(1, Timestamp.valueOf(userStory.createDate())); ps.setLong(2, userStory.numberOfViews()); ps.setString(3, userStory.title()); ps.setString(4, userStory.body()); ps.setLong(5, userStory.userId()); return ps; }, keyHolder); var gener...
[SugarColumn(ColumnDescription = "ID", IsPrimaryKey = true, IsIdentity = true)] public virtual long Id { get; set; } [SugarColumn(IsOnlyIgnoreUpdate = true, IsNullable = true, InsertServerTime = true)] public virtual DateTime CreatedAt { get; set; } ...