在sqlite3数据库中插入datetime错误

Question

I have a pandas dataframe with the following data types

var1            object
var2        datetime64[ns]
var3             object
var4            object
var5             int64
var6            float64

my schema in the sqlite3 data base is

CREATE TABLE IF NOT EXISTS "table_name" (
"var1" TEXT,
"var2" DATETIME,
"var3" TEXT,
"var4" TEXT,
"var5" INT,
"var6" REAL
);

my query in python looks lite this

query = 'insert into first_north4 (var1, var2, var3, var4, var5, var6) values (?, ?, ?, ?, ?, ?)'
values = [tuple(x) for x in df.values]
cur.executemany(query, values)

When executing the query I get this error msg

sqlite3.InterfaceError: Error binding parameter 1 - probably unsupported type.

This is the datetime that fails, I can't figure out why

Answer 1

From the sqlite datatypes doc :

2.2. Date and Time Datatype

SQLite does not have a storage class set aside for storing dates and/or times. Instead, the built-in Date And Time Functions of SQLite are capable of storing dates and times as TEXT, REAL, or INTEGER values:

• TEXT as ISO8601 strings ("YYYY-MM-DD HH:MM:SS.SSS").
• REAL as Julian day numbers, the number of days since noon in Greenwich on November 24, 4714 BC according to the proleptic
  Gregorian calendar.
• INTEGER as Unix Time, the number of seconds since 1970-01-01 00:00:00 UTC.

Applications can chose to store dates and times in any of these formats and freely convert between formats using the built-in date and time functions.

One option would be to convert var2 to a string before db insert (thus preserving the DATETIME datatype in the database) as described here . There are other options, and a search on this forum for "datetime64 sqlite" should provide other approaches.

Answer 2

I found a working solution for me (regarding date object), hopefully this will help somebody else in the future. Fully working example below in python3

import pandas as pd
import datetime as dt
import sqlite3

# est conn (creates db if not exist)
db = 'db_test.db'
conn=sqlite3.connect(db,
detect_types=sqlite3.PARSE_DECLTYPES|sqlite3.PARSE_COLNAMES)
cur = conn.cursor()

# create table
query='CREATE TABLE IF NOT EXISTS test(i INT, f REAL, d DATE)'
cur.execute(query)

# some specific datatypes to dataframe
i = [4 ,2 ,44]
f=[1.23,123.2,2.2222]
d = [dt.date.today(),dt.date.today(),dt.date.today()]
df = pd.DataFrame(data=[i,f,d],index = ['i','f','d']).T
print(df)
print(df.dtypes)
print(type(df['i'].values[0]))
print(type(df['f'].values[0]))
print(type(df['d'].values[0]))

# insert
query = 'insert into test (i, f, d) values (? ,?, ?)'
values = [tuple(x) for x in df.values]
print(values)
cur.executemany(query, values)
conn.commit()

# test types when querying the db
query = cur.execute('SELECT * from test')
cols = [column[0] for column in query.description]
data = pd.DataFrame.from_records(data=query.fetchall(), columns=cols)
print(data)
print(data.dtypes)
print(type(data['i'].values[0]))
print(type(data['f'].values[0]))
print(type(data['d'].values[0]))

# close conn
cur.close()
conn.close()