如何将 Pandas DataFrame 更新到 Microsoft SQL Server 表? [英] How to upsert pandas DataFrame to Microsoft SQL Server table?

问题描述

我想将我的 Pandas DataFrame 插入到 SQL Server 表中.这个问题对 PostgreSQL 有一个可行的解决方案，但 T-SQL 没有 ON CONFLICTINSERT 的变体.我怎样才能为 SQL Server 完成同样的事情?

I would like to upsert my pandas DataFrame into a SQL Server table. This question has a workable solution for PostgreSQL, but T-SQL does not have an ON CONFLICT variant of INSERT. How can I accomplish the same thing for SQL Server?

推荐答案

有两个选项:

1. 使用 MERGE 语句代替 INSERT ... ON CONFLICT.
2. 使用带有 JOIN 和条件 INSERT 的 UPDATE 语句.

1. Use a MERGE statement instead of INSERT ... ON CONFLICT.
2. Use an UPDATE statement with a JOIN, followed by a conditional INSERT.

T-SQL MERGE 文档 说:

性能提示:当两个表具有复杂的匹配特征混合时，为 MERGE 语句描述的条件行为效果最佳.例如，如果一行不存在则插入，或者如果匹配则更新一行.当简单地根据另一个表的行更新一个表时，使用基本的 INSERT、UPDATE 和 DELETE 语句提高性能和可伸缩性.

Performance Tip: The conditional behavior described for the MERGE statement works best when the two tables have a complex mixture of matching characteristics. For example, inserting a row if it doesn't exist, or updating a row if it matches. When simply updating one table based on the rows of another table, improve the performance and scalability with basic INSERT, UPDATE, and DELETE statements.

在许多情况下，简单地使用单独的 UPDATE 和 INSERT 语句更快、更简单.

In many cases it is faster and less complicated to simply use the separate UPDATE and INSERT statements.

engine = sa.create_engine(
    connection_uri, fast_executemany=True, isolation_level="SERIALIZABLE"
)

with engine.begin() as conn:
    # step 0.0 - create test environment
    conn.execute(sa.text("DROP TABLE IF EXISTS main_table"))
    conn.execute(
        sa.text(
            "CREATE TABLE main_table (id int primary key, txt varchar(50))"
        )
    )
    conn.execute(
        sa.text(
            "INSERT INTO main_table (id, txt) VALUES (1, 'row 1 old text')"
        )
    )
    # step 0.1 - create DataFrame to UPSERT
    df = pd.DataFrame(
        [(2, "new row 2 text"), (1, "row 1 new text")], columns=["id", "txt"]
    )

    # step 1 - upload DataFrame to temporary table
    df.to_sql("#temp_table", conn, index=False, if_exists="replace")

    # step 2 - merge temp_table into main_table
    conn.execute(
        sa.text("""\
            UPDATE main SET main.txt = temp.txt
            FROM main_table main INNER JOIN #temp_table temp
                ON main.id = temp.id
            """
        )
    )
    conn.execute(
        sa.text("""\
            INSERT INTO main_table (id, txt) 
            SELECT id, txt FROM #temp_table
            WHERE id NOT IN (SELECT id FROM main_table) 
            """
        )
    )

    # step 3 - confirm results
    result = conn.execute(sa.text("SELECT * FROM main_table ORDER BY id")).fetchall()
    print(result)  # [(1, 'row 1 new text'), (2, 'new row 2 text')]

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