sqlalchemy创建自定义cte做临时表功能

代码示例：

import sqlalchemy as sa
# 自定义列表
rows = [('BTC_USD', '0_4', 1),
        ('BTC_USD', '4_8', 2),
        ('BTC_USD', '8_12', 4),
        ('BCH_USD', '0_4', 10),
        ('BCH_USD', '4_8', 8),
        ('BCH_USD', '8_12', 6),
        ('LTC_USD', '0_4', 7),
        ('LTC_USD', '4_8', 8),
        ('LTC_USD', '8_12', 9)
       ]

stmts = [
    # @NOTE: optimization to reduce the size of the statement:
    # make type cast only for first row, for other rows DB engine will infer
    sa.select([
        sa.cast(sa.literal(i), sa.String).label("symbol"),
        sa.cast(sa.literal(v), sa.String).label("duration"),
        sa.cast(sa.literal(d), sa.Integer).label("rate"),
    ]) if idx == 0 else
    sa.select([sa.literal(i), sa.literal(v), sa.literal(d)])  # no type cast

    for idx, (i, v, d) in enumerate(rows)
]
subquery = sa.union_all(*stmts)
print(subquery)
# Choose one option below.
# I personally prefer B because one could reuse the CTE multiple times in the same query

subquery = subquery.cte(name="temp_table")

print(subquery.c.duration)