poster的基本使用

⚠️： 大部分结尾要加引号 开头要加 \

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enter bd：

    psql -h host_name -p port_name db_name user_name

quit database:  \q

search all db tables:    \dt

search table frame:     \d table_name

alter the column type of table:

    ALTER TABLE table_name ALTER COLUMN column_name TYPE type_name;

alter table_name:

    ALTER TABLE table_name RENAME TO new_name;

add column in a table:

    ALTER TABLE  table_name ADD column_name dataType;

alter the column_type of a column in table:

    ALTER TABLE table_name ALTER COLUMN column_name TYPE dataType;

delete all data of a table:

    DELETE FROM table_name;

delete some data of a table:

    eg: DELETE FROM table_name WHERE time in (SELECT time from table_name ORDER BY time limit 3);

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used in python:

import psycopg2

conn= psycopg2.connect(database='imd', password='imd', user='imd', host='192.168.3.24', port='5432')

cur= conn.cursor()

sql= "SELECT * FROM coins_1m"

df= pd.read_sql(sql, conn,)

cur.close()

conn.close()