我需要用一个查询插入多行(行数不是常量),所以我需要像这样执行查询:

INSERT INTO t (a, b) VALUES (1, 2), (3, 4), (5, 6);

我唯一知道的办法就是

args = [(1,2), (3,4), (5,6)]
args_str = ','.join(cursor.mogrify("%s", (x, )) for x in args)
cursor.execute("INSERT INTO t (a, b) VALUES "+args_str)

但我想要更简单的方法。


当前回答

如果您正在使用SQLAlchemy,则不需要手工制作字符串,因为SQLAlchemy支持为单个INSERT语句生成多行VALUES子句:

rows = []
for i, name in enumerate(rawdata):
    row = {
        'id': i,
        'name': name,
        'valid': True,
    }
    rows.append(row)
if len(rows) > 0:  # INSERT fails if no rows
    insert_query = SQLAlchemyModelName.__table__.insert().values(rows)
    session.execute(insert_query)

其他回答

另一种有效的方法是将rows作为1参数传递给insert, 也就是数组的json对象。

例如,你传递的论点:

[ {id: 18, score: 1}, { id: 19, score: 5} ]

它是一个数组,其中可以包含任意数量的对象。 然后你的SQL看起来像这样:

INSERT INTO links (parent_id, child_id, score) 
SELECT 123, (r->>'id')::int, (r->>'score')::int 
FROM unnest($1::json[]) as r 

注意:你的postgress必须足够新,才能支持json

如果你想在一个insert语句中插入多行(假设你没有使用ORM),到目前为止对我来说最简单的方法是使用字典列表。这里有一个例子:

 t = [{'id':1, 'start_date': '2015-07-19 00:00:00', 'end_date': '2015-07-20 00:00:00', 'campaignid': 6},
      {'id':2, 'start_date': '2015-07-19 00:00:00', 'end_date': '2015-07-20 00:00:00', 'campaignid': 7},
      {'id':3, 'start_date': '2015-07-19 00:00:00', 'end_date': '2015-07-20 00:00:00', 'campaignid': 8}]

conn.execute("insert into campaign_dates
             (id, start_date, end_date, campaignid) 
              values (%(id)s, %(start_date)s, %(end_date)s, %(campaignid)s);",
             t)

正如你所看到的,只会执行一个查询:

INFO sqlalchemy.engine.base.Engine insert into campaign_dates (id, start_date, end_date, campaignid) values (%(id)s, %(start_date)s, %(end_date)s, %(campaignid)s);
INFO sqlalchemy.engine.base.Engine [{'campaignid': 6, 'id': 1, 'end_date': '2015-07-20 00:00:00', 'start_date': '2015-07-19 00:00:00'}, {'campaignid': 7, 'id': 2, 'end_date': '2015-07-20 00:00:00', 'start_date': '2015-07-19 00:00:00'}, {'campaignid': 8, 'id': 3, 'end_date': '2015-07-20 00:00:00', 'start_date': '2015-07-19 00:00:00'}]
INFO sqlalchemy.engine.base.Engine COMMIT

执行任意接受数组的元组

https://www.postgresqltutorial.com/postgresql-python/insert/

    """ array of tuples """
    vendor_list = [(value1,)]

    """ insert multiple vendors into the vendors table  """
    sql = "INSERT INTO vendors(vendor_name) VALUES(%s)"
    conn = None
    try:
        # read database configuration
        params = config()
        # connect to the PostgreSQL database
        conn = psycopg2.connect(**params)
        # create a new cursor
        cur = conn.cursor()
        # execute the INSERT statement
        cur.executemany(sql,vendor_list)
        # commit the changes to the database
        conn.commit()
        # close communication with the database
        cur.close()
    except (Exception, psycopg2.DatabaseError) as error:
        print(error)
    finally:
        if conn is not None:
            conn.close()

所有这些技术在Postgres术语中都被称为“扩展插入”,截至2016年11月24日,它仍然比psychopg2的executemany()和这个线程中列出的所有其他方法快得多(在得到这个答案之前我尝试过)。

下面是一些不使用cur.mogrify的代码,很好,很简单:

valueSQL = [ '%s', '%s', '%s', ... ] # as many as you have columns.
sqlrows = []
rowsPerInsert = 3 # more means faster, but with diminishing returns..
for row in getSomeData:
        # row == [1, 'a', 'yolo', ... ]
        sqlrows += row
        if ( len(sqlrows)/len(valueSQL) ) % rowsPerInsert == 0:
                # sqlrows == [ 1, 'a', 'yolo', 2, 'b', 'swag', 3, 'c', 'selfie' ]
                insertSQL = 'INSERT INTO "twitter" VALUES ' + ','.join(['(' + ','.join(valueSQL) + ')']*rowsPerInsert)
                cur.execute(insertSQL, sqlrows)
                con.commit()
                sqlrows = []
insertSQL = 'INSERT INTO "twitter" VALUES ' + ','.join(['(' + ','.join(valueSQL) + ')']*len(sqlrows))
cur.execute(insertSQL, sqlrows)
con.commit()

但需要注意的是,如果可以使用copy_from(),则应该使用copy_from;)

来自Psycopg2教程页面Postgresql.org的一个片段(见底部):

我想向您展示的最后一项是如何使用字典插入多行。如果你有以下情况:

namedict = ({"first_name":"Joshua", "last_name":"Drake"},
            {"first_name":"Steven", "last_name":"Foo"},
            {"first_name":"David", "last_name":"Bar"})

你可以很容易地将这三行都插入到字典中:

cur = conn.cursor()
cur.executemany("""INSERT INTO bar(first_name,last_name) VALUES (%(first_name)s, %(last_name)s)""", namedict)

它没有节省多少代码,但它确实看起来更好。