[英]How to conduct SQL queries on multiple .db files and store the results in a .csv?
我的 Google Drive 上存儲了大約 100.db 文件,我想在這些文件上運行相同的 SQL 查詢。 我想將這些查詢結果存儲在單個.csv 文件中。
我設法使用以下代碼將單個 SQL 查詢的結果寫入 a.csv 文件,但我無法使其適用於多個文件。
conn = sqlite3.connect('/content/drive/My Drive/Data/month_2014_01.db')
df = pd.read_sql_query("SELECT * FROM messages INNER JOIN users ON messages.id = users.id WHERE text LIKE '%house%'", conn)
df.to_csv('/content/drive/My Drive/Data/Query_Results.csv')
根據這篇文章,這是我迄今為止用來嘗試使其適用於所有文件的代碼。
databases = []
directory = '/content/drive/My Drive/Data/'
for filename in os.listdir(directory):
flname = os.path.join(directory, filename)
databases.append(flname)
for database in databases:
try:
with sqlite3.connect(database) as conn:
conn.text_factory = str
cur = conn.cursor()
cur.execute(row["SELECT * FROM messages INNER JOIN users ON messages.id = users.id WHERE text LIKE '%house%'"])
df.loc[index,'Results'] = cur.fetchall()
except sqlite3.Error as err:
print ("[INFO] %s" % err)
但這會給我一個錯誤: TypeError: tuple indices must be integers or slices, not str 。 我顯然做錯了什么,我將非常感謝任何指向答案的提示。
考慮構建一個數據幀列表,然后使用pandas.concat
將它們連接到一個數據幀中:
gdrive = "/content/drive/My Drive/Data/"
sql = """SELECT * FROM messages
INNER JOIN users ON messages.id = users.id
WHERE text LIKE '%house%'
"""
def build_df(db)
with sqlite3.connect(os.path.join(gdrive, db)) as conn:
df = pd.read_sql_query(sql, conn)
return df
# BUILD LIST OF DFs WITH LIST COMPREHENSION
df_list = [build_df(db) for db in os.listdir(gdrive) if db.endswith('.db')]
# CONCATENATE ALL DFs INTO SINGLE DF FOR EXPORT
final_df = pd.concat(df_list, ignore_index = True)
final_df.to_csv(os.path.join(gdrive, 'Query_Results.csv'), index = False)
更好的是,將 SQLite 的ATTACH DATABASE
和 append 查詢結果考慮到主表中。 這也避免了使用繁重的數據科學第三方庫pandas
來滿足簡單的數據遷移需求。 此外,您可以將所有數據庫數據保存在 SQLite 中,而無需擔心數據類型轉換和 i/o 傳輸問題。
import csv
import sqlite3
with sqlite3.connect(os.path.join(gdrive, 'month_2014_01')) as conn:
# CREATE MASTER TABLE
cur = conn.cursor()
cur.execute("DROP TABLE IF EXISTS master_query")
cur.execute("""CREATE TABLE master_query AS
SELECT * FROM tmp.messages
INNER JOIN tmp.users
ON tmp.messages.id = tmp.users.id
WHERE text LIKE '%house%'
""")
conn.commit()
# ITERATIVELY ATTACH AND APPEND RESULTS
for db in os.listdir(gdrive):
if db.endswith('.db'):
cur.execute("ATTACH DATABASE ? AS tmp", [db])
cur.execute("""INSERT INTO master_query
SELECT * FROM tmp.messages
INNER JOIN tmp.users
ON tmp.messages.id = tmp.users.id
WHERE text LIKE '%house%'
""")
cur.execute("DETACH DATABASE tmp")
conn.commit()
# WRITE TUPLE OF ROWS TO CSV
data = cur.execute("SELECT * FROM master_query")
with open(os.path.join(gdrive, 'Query_Results.csv'), 'wb') as f:
writer = csv.writer(f)
writer.writerow([i[0] for i in cur.description]) # HEADERS
writer.writerows(data) # DATA
cur.close()
聲明:本站的技術帖子網頁,遵循CC BY-SA 4.0協議,如果您需要轉載,請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.