python - 如果表为空则执行 INSERT 多个值 POSTGRES

Question

我正在尝试在 postgres 表中添加一些默认值。我可以添加 1 个值，但我想添加 5 个默认值。我在下面尝试过此操作，但它仅创建一个值，因为插入第一个值后，空条件不再有效。

records_to_insert = [( 1,'foo', 30, 2, True),
                   ( 2,'bar', 60, 3, False),
                   ( 3,'hero', 95, 2, False),
                   ( 4,'borth', 45, 1, True),
                   ( 5,'here', 30, 2, True)]
sql_insert_query = """ INSERT INTO tester (id, name, time, rating,others)
                SELECT %s,%s,%s,%s,%s
                WHERE NOT EXISTS (SELECT * FROM tester) """
cursor = connection.cursor()
#executemany() to insert 3 rows
result  = cursor.executemany(sql_insert_query, records_to_insert)

我使用的是python3和postgres10.5。我还看过this , this和 this但没有骰子。

Answer 1

使用psycopg2.extras.execute_values(cur, sql, argslist, template=None, page_size=100)

Execute a statement using VALUES with a sequence of parameters. Parameters:

• cur – the cursor to use to execute the query.
• sql – the query to execute. It must contain a single %s placeholder, which will be replaced by a VALUES list. (...)

您应该重新编写查询以使用VALUES:

from psycopg2.extras import execute_values

sql_insert_query = """ 
    INSERT INTO tester (id, name, time, rating, others)
    SELECT * FROM (VALUES %s) s
    WHERE NOT EXISTS (SELECT 1 FROM tester) """
execute_values(cursor, sql_insert_query, records_to_insert)