openGauss每日一练第13天|《openGauss导入数据》学习心得体会和课后练习

openGauss每日一练第13天|《openGauss导入数据》学习心得体会和课后练习

学习openGauss导入数据

课程学习

连接数据库

#第一次进入等待15秒
#数据库启动中...
su - omm
gsql -r

1.通过INSERT语句直接写入数据

CREATE TABLE reason_t1
(
r_reason_sk integer,
r_reason_id character(16),
r_reason_desc character(100)
);
insert into reason_t1 values(1, 'AAAAAAAABAAAAAAA', 'reason1');

–没有数值的字段将被填充为字段的缺省值

insert into reason_t1 values(1, 'AAAAAAAABAAAAAAA');

–明确字段为缺省值

insert into reason_t1 values(1, 'AAAAAAAABAAAAAAA', DEFAULT);

–明确整行为缺省值

insert into reason_t1 DEFAULT VALUES;
select * from reason_t1;

–指定表插入数据到当前表

CREATE TABLE reason_t2
(
r_reason_sk integer,
r_reason_id character(16),
r_reason_desc character(100)
);

–将查询结果作为插入的数据

INSERT INTO reason_t2 SELECT * FROM reason_t1;
select * from reason_t2;

2.使用合并方式更新和插入数据

–创建源表products，并插入数据

CREATE TABLE products
( product_id INTEGER,
product_name VARCHAR2(60),
category VARCHAR2(60)
);
INSERT INTO products VALUES
(1502, 'olympus camera', 'electrncs'),
(1601, 'lamaze', 'toys'),
(1666, 'harry potter', 'toys'),
(1700, 'wait interface', 'books');

–创建目标表newproducts，并插入数据

CREATE TABLE newproducts
( product_id INTEGER,
product_name VARCHAR2(60),
category VARCHAR2(60)
);
INSERT INTO newproducts VALUES
(1501, 'vivitar 35mm', 'electrncs'),
(1502, 'olympus ', 'electrncs'),
(1600, 'play gym', 'toys'),
(1601, 'lamaze', 'toys'),
(1666, 'harry potter', 'dvd');

–使用MERGE INTO 语句将源表products的数据合并至目标表newproducts

MERGE INTO newproducts np
USING products p
ON (np.product_id = p.product_id )
WHEN MATCHED THEN
UPDATE SET np.product_name = p.product_name, np.category = p.category
WHEN NOT MATCHED THEN
INSERT VALUES (p.product_id, p.product_name, p.category) ;

–查询合并后的目标表newproducts。

SELECT * FROM newproducts

3.使用COPY实现表和文件间的拷贝

–将表数据输出到stdout

copy reason_t1 to stdout;

–将表数据拷贝到文件

copy reason_t1 to '/home/omm/reason.dat';
CREATE TABLE reason_t3 (LIKE reason_t1);

–将数据从文件拷贝到表

copy reason_t3 from '/home/omm/reason.dat';
select * from reason_t3;

课程作业

1.创建表1并在表中插入数据，分别指定字段和整行为缺省值

create table test (id int,name varchar(20) default('noname'));
insert into test values(1,default);
insert into test DEFAULT VALUES;
select * from test;
omm=# create table test (id int,name varchar(20) default('noname'));
CREATE TABLE
omm=# 
omm=# 
omm=# insert into test values(1,default);
INSERT 0 1
omm=# select * from test;
 id |  name  
----+--------
  1 | noname
(1 row)

omm=# insert into test DEFAULT VALUES;
INSERT 0 1
omm=# select * from test;
 id |  name  
----+--------
  1 | noname
    | noname
(2 rows)

2.创建表2并将表1的数据全部导入表2中

create table test2 as select * from test1;
or
create table test2 (id int,name varchar(20) default('noname'));
insert into test2 select * from test;

3.创建表3和表4，并合并两个表的数据到表3

create table test3 (id int,name varchar(20));
create table test4 (id int,name varchar(20));

insert into test3 values(1,'yanwei'),(2,'junjun'),(3,'junjun');
insert into test4 values(1,'yanwei'),(2,'dave'),(4,'happy');

omm=# select * from test3;
 id |  name  
----+--------
  1 | yanwei
  2 | junjun
  3 | junjun
(3 rows)

omm=# select * from test4;
 id |  name  
----+--------
  1 | yanwei
  2 | dave
  4 | happy
(3 rows)

MERGE INTO test4 n
USING test3 m
ON (n.id = m.id )
WHEN MATCHED THEN
UPDATE SET n.name = m.name
WHEN NOT MATCHED THEN
INSERT VALUES (m.id, m.name) ;
omm=# select * from test4;
 id |  name  
----+--------
  4 | happy
  1 | yanwei
  2 | junjun
  3 | junjun
(4 rows)

4.将表3的数据输出到文件，再将文件中的数据导入到表5

copy test3 to '/home/omm/test3.dat';
CREATE TABLE test5 (LIKE test3);
copy test5 from '/home/omm/test3.dat';
select * from test5;


omm=# copy test3 to '/home/omm/test3.dat';
COPY 3
omm=# CREATE TABLE test5 (LIKE test3);
CREATE TABLE
omm=# copy test5 from '/home/omm/test3.dat';
COPY 3
omm=# select * from test5;
 id |  name  
----+--------
  1 | yanwei
  2 | junjun
  3 | junjun
(3 rows)