需要帮助来理解SQL查询(oracle10g)

Question

我是SQL的新手,在理解这个SQL语句中的部分时几乎无需帮助

select BUY_VALUE,
    SELL_VALUE,
    RATE_DAY,
    RATE_TIME
from ( SELECT TRIM (b.ticker),
           TRIM (TO_CHAR (b.buy_value, '9999999.99')) BUY_VALUE,
           TRIM (TO_CHAR (b.sell_value, '9999999.99')) SELL_VALUE,
           b.currency, 
           TO_CHAR (TRUNC (SYSDATE), 'YYYYMMDD') rate_day,
           TO_CHAR (SYSDATE, 'HH24MISS') rate_time 
         FROM portal.gpb_bank_quotes b
         WHERE b.ticker = 'GAZP'
     )

1. 什么是b(b.buy_value)？
2. FROM portal.gpb_bank_quotes - 是那个表名吗？它是否有可能与之界定.
3. 啊太难了///

提前致谢

Answer 1

1. b是表别名为portal.gpb_bank_quotes.这很方便,所以你不必打字portal.gpb_bank_quotes.buy_value等.

2. 是. portal是架构,是该架构gpb_bank_quotes中的表.