如何检查主键值是否存在于另一个表中？

SELECT EXISTS (
    SELECT 1 FROM TableB WHERE TableB.id = TableA.id
) AS isExists FROM TableA WHERE TableA.id = ?;

SELECT COUNT(*) > 0 AS isExists FROM TableA 
LEFT JOIN TableB ON TableA.id = TableB.id 
WHERE TableA.id = ?;

SELECT id IN (SELECT id FROM TableB) AS isExists FROM TableA WHERE TableA.id = ?;

from sqlalchemy import create_engine, Table, Column, Integer, MetaData, select

engine = create_engine('your_database_connection_string')
metadata = MetaData()

TableA = Table('TableA', metadata,
    Column('id', Integer, primary_key=True)
)

TableB = Table('TableB', metadata,
    Column('id', Integer, primary_key=True)
)

with engine.connect() as conn:
    id_to_check = 123
    stmt = select(TableA).where(TableA.c.id == id_to_check)
    result = conn.execute(stmt).fetchone()
    
    if result:
        exists_stmt = select(1).where(TableB.c.id == id_to_check)
        exists_result = conn.execute(exists_stmt).scalar()
        print(f"ID {id_to_check} exists in TableB: {exists_result}")
    else:
        print(f"ID {id_to_check} does not exist in TableA")