How to use the SQLite querying language?

To use SQLite query statements, follow these steps:

1. Open or connect to a SQLite database: use the libraries or tools provided by SQLite to open a SQLite database file, or connect to the database using a connection string.
2. Write a query statement: Use the query statement syntax of SQLite to write the query statement to be executed. Query statements typically start with the SELECT keyword followed by the list of fields to be queried, table name, filter conditions, etc.
3. Execute the query statement: Using the appropriate SQLite library or tool, execute the query statement. Executing the query statement will retrieve data from the database and return the result set.
4. Process query results: Depending on the needs, process and parse the query results. Utilize APIs provided by programming languages to handle the result set, such as storing results in variables, arrays, or objects, or performing further calculations, filtering, or presenting the results.
5. Close the database connection: Remember to close the database connection after completing the query operation to release resources.

Below is a basic example demonstrating how to execute query statements using the sqlite3 library in Python.

import sqlite3

# 连接到SQLite数据库
conn = sqlite3.connect('example.db')

# 创建一个游标对象
cursor = conn.cursor()

# 编写查询语句
query = "SELECT * FROM my_table"

# 执行查询语句
cursor.execute(query)

# 获取查询结果
results = cursor.fetchall()

# 处理查询结果
for row in results:
    print(row)

# 关闭数据库连接
conn.close()

In the above example, we first connected to the SQLite database using the sqlite3 library. Next, we created a cursor object to perform query operations. Then, we wrote the query statement and executed it using the execute() method. Finally, we used the fetchall() method to retrieve all query results and processed them. Finally, we closed the database connection to release resources.