[英]Execute a query for multiple sets of parameters with psycopg2
我有一個要查詢的表,但我想進行許多特定的查詢並返回滿足其條件的任何結果的表,並忽略不存在的查詢。
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()
希望這說明了我在這里想要實現的目標......
我想執行一系列 select 語句,每個語句都有一對參數。 如果那對參數在數據庫中,則 append 將其添加到結果表中。
是在for-loop
中手動執行此操作的唯一方法嗎?
在循環中執行許多查詢不是一個好主意。 使用公用表表達式將多對參數傳遞給單個查詢並獲得所有參數的結果,就像這個 Postgres 示例一樣。
Python 代碼:
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()
一個簡單直觀的解決方案是對 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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