mysql load data處理空字符串導入數據庫默認變成0的情況

會發生這種情況，一定是字段爲int或者float類型，它會把空字符串默認爲0，varchar則會還是空字符串

解決辦法一般爲兩個：第一個把所有空字符串替換爲\N

import re

with open("F:\\factor_db\\test_new", 'a') as g:
    for line in open("F:\\factor_db\\test_old.txt", 'r'):
        b = list(set(re.findall('\t+', line)))
        b.sort(key = lambda i:len(i),reverse=True)
        line = line.replace('\t\n', '\t\\N\n')
        if max([len(i) for i in b])==1:
            g.write(line)
        else:
            for i in b:
                templen=len(i)
                line=line.replace(i, '\t\\N'*(templen-1)+'\t')
            g.write(line)

 test_old.txt是直接從mysql生成的文本，test_new是最後處理成新的文本，然後直接

load data infile 'F:/factor_db/test_new' into table t_stock_factor_barra fields terminated by '\t' lines terminated by '\r\n' ignore 1 lines

數據庫直接就是null

推薦第二個：

load data infile 'F:/factor_db/barra_test' into table t_stock_factor_barra fields terminated by '\t' lines terminated by '\r\n' ignore 1 lines
(`full_insID`,`date`,@`beta`,@`book_to_price_ratio`,@`earnings_yield`,@`growth`,@`leverage`,@`liquidity`,@`momentum`,@`non_linear_size`,@`residual_volatil

ity`,@`size`)
set
`beta` = NULLif(@beta,''),
`book_to_price_ratio` = NULLif(@book_to_price_ratio,''),
`earnings_yield` = NULLif(@earnings_yield,''),
`growth` = NULLif(@growth,''),
`leverage` = NULLif(@leverage,''),
`liquidity` = NULLif(@liquidity,''),
`momentum` = NULLif(@momentum,''),
`non_linear_size` = NULLif(@non_linear_size,''),
`residual_volatility` = NULLif(@residual_volatility,''),
`size` = NULLif(@size,'')
;

F:/factor_db/barra_test是要導入的文檔

(`full_insID`,`date`,@`beta`,@`book_to_price_ratio`,@`earnings_yield`,@`growth`,@`leverage`,@`liquidity`,@`momentum`,@`non_linear_size`,@`residual_volatil

ity`,@`size`)

是數據庫表字段名稱，一定要按順序寫

加@的就是判斷有空字符串，直接存爲null的，下面跟上`字段名` = NULLif(@字段名,'')這句話就能完成了