[英]Execute a query for multiple sets of parameters with psycopg2
我有一个要查询的表,但我想进行许多特定的查询并返回满足其条件的任何结果的表,并忽略不存在的查询。
data = (
(1, '2020-11-19'),
(1, '2020-11-20'),
(1, '2020-11-21'),
(2, '2020-11-19'),
(2, '2020-11-20'),
(2, '2020-11-21')
)
string = """
SELECT * FROM my_schema.my_table
WHERE my_schema.my_table.song_id = %s
AND my_schema.my_table.date = %s;
"""
execute_values(cursor, string, data)
results = cursor.fetchall()
希望这说明了我在这里想要实现的目标......
我想执行一系列 select 语句,每个语句都有一对参数。 如果那对参数在数据库中,则 append 将其添加到结果表中。
是在for-loop
中手动执行此操作的唯一方法吗?
在循环中执行许多查询不是一个好主意。 使用公用表表达式将多对参数传递给单个查询并获得所有参数的结果,就像这个 Postgres 示例一样。
Python 代码:
data = (
(1, '2020-11-19'),
(1, '2020-11-20'),
(1, '2020-11-21'),
(2, '2020-11-19'),
(2, '2020-11-20'),
(2, '2020-11-21')
)
query = """
with data(song_id, date) as (
values %s
)
select t.*
from my_table t
join data d
on t.song_id = d.song_id and t.date = d.date::date
"""
execute_values(cursor, query, data)
results = cursor.fetchall()
一个简单直观的解决方案是对 Tuple 使用“ IN ”子句
即 (col1, col2) in ( (data11, data12), (data21, data22) )例如
SELECT * FROM BOOKINGS WHERE (user_id,booked_at) in ((1, '2020-11-19'),(2, '2020-11-20') );"
import psycopg2
from psycopg2.extras import execute_values
import pandas as pd
# Ref - https://uibakery.io/sql-playground
connection = psycopg2.connect(host='psql-mock-database-cloud.postgres.database.azure.com', user='zvgyzkbybtzsnmvqkwzqmogy@psql-mock-database-cloud', password='tixzlbnnrjlbczfuzbmdwsxd', dbname='booking1665772869599ofknbwmmpsmnffue', port=5432)
data = (
(125, '2021-11-18T08:08:59.839Z'),
(28, '2021-11-17T20:01:02.244Z'),
(78, '2021-11-17T15:57:27.186Z'))
string = "SELECT * FROM BOOKINGS WHERE (user_id,booked_at) in ( %s );"
with connection.cursor() as cursor:
execute_values(cursor, string, data)
results = cursor.fetchall()
col_names = [desc[0] for desc in cursor.description]
df = pd.DataFrame(results, columns=col_names)
df
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