如何使用 Python 迭代创建 UNION ALL SQL 语句？

Question

我正在连接到 Snowflake 以查询来自 Snowflake 的视图 table 的行计数数据。我也在查询与 View table 相关的元数据。我的查询如下所示。我想知道我是否可以使用 python 遍历 UNION ALL 语句？当我尝试运行我的以下查询时，我收到一条错误消息，提示“view_table_3”不存在。

提前感谢您的时间和努力！

查询获取 Snowflake 视图的行数 table（带元数据）

view_tables=['view_table1','view_table2','view_table3','view_table4']

print(f""" SELECT * FROM (SELECT TABLE_SCHEMA,TABLE_NAME,CREATED,LAST_ALTERED FROM SCHEMA='INFORMATION_SCHEMA.VIEWS' WHERE TABLE_SCHEMA='MY_SCHEMA' AND TABLE_NAME IN ({','.join("'" +x+ "'" for x in view_tables)})) t1

LEFT JOIN
(SELECT 'view_table1' table_name2, count(*) as view_row_count from MY_DB.SCHEMA.view_table1
UNION ALL SELECT {','.join("'" +x+ "'" for x in view_tables[1:])},count(*) as view_row_count from MY_DB.SCHEMA.{','.join("" +x+ "" for x.replace("'"," ") in view_tables)})t2
on t1.TABLE_NAME =t2.table_name2 """)

Answer 1

如果要动态联合，请将整个 SELECT 查询放入生成器中，然后用 ' UNION ' 加入它们。

sql = f'''SELECT * FROM INFORMATION_SCHEMA.VIEWS AS v
LEFT JOIN (
    {' UNION '.join(f"SELECT '{table}' AS table_name2, COUNT(*) AS view_row_count FROM MY_SCHEMA.{table}" for table in view_tables)}
) AS t2 ON v.TABLE_NAME = t2.table_name2
WHERE v.TABLE_NAME IN ({','.join(f"'{table}'" for table in view_tables)})
'''
print(sql);

如何使用 Python 迭代创建 UNION ALL SQL 语句？

How to iteratively create UNION ALL SQL statement using Python?

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