我可以添加功能对重复密钥更新

Question

我有一个函数使用CVS进口商有问题的原代码如下插入数据到MySQL：

{ 
     $sql = "LOAD DATA INFILE '".@mysql_escape_string($this->file_name). 
      "' INTO TABLE `".$this->table_name. 
      "` FIELDS TERMINATED BY '".@mysql_escape_string($this->field_separate_char). 
      "' OPTIONALLY ENCLOSED BY '".@mysql_escape_string($this->field_enclose_char). 
      "' ESCAPED BY '".@mysql_escape_string($this->field_escape_char). 
      "' ". 
      ($this->use_csv_header ? " IGNORE 1 LINES " : "") 
      ."(`".implode("`,`", $this->arr_csv_columns)."`)"; 
     $res = mysql_query($sql); 
     $this->error = mysql_error(); 
    } 

我的问题是，我该怎么办，如果只有更新记录到该表而不重新插入新记录，因为我想插入多个记录，然后再次上载它们，但是使用字段＃LL，其首先将为空，然后更新将取值

Answer 1

看起来像MySQL has support for temporary tables，所以一种解决方案是插入CSV d ata到临时表中，然后将其加入永久数据以确定要更新哪些行。

简单的例子（假设你的目标表被称为datatable，有一个主键叫做data_id，和列field_a和field_b）：

CREATE TEMPORARY TABLE temp_bulk_inserted_datatable LIKE datatable; 

LOAD DATA INFILE '/path/to/data.csv' INTO TABLE temp_bulk_inserted_datatable; 

-- Update rows that already exist with new data from the file 
UPDATE 
    datatable as OLD 
JOIN 
    -- Inner Join, so that only matching rows will be touched 
    temp_bulk_inserted_datatable as NEW 
    ON OLD.data_id = NEW.data_id 
SET 
    OLD.field_a = NEW.field_a, 
    OLD.field_b = NEW.field_b; 

-- Insert new rows from the CSV file which don't yet exist 
INSERT INTO datatable 
    (data_id, field_a, field_b) 
SELECT 
    NEW.data_id, NEW.field_a, NEW.field_b 
FROM 
    temp_bulk_inserted_datatable as NEW 
LEFT JOIN 
    -- Left Outer Join: we want to know about non-matches... 
    datatable as OLD 
    ON OLD.data_id = NEW.data_id 
WHERE 
    -- ...in fact, we want ONLY the non-matches 
    OLD.data_id IS NULL; 

DROP TABLE temp_bulk_inserted_datatable; 

（请注意，我不实际使用MySQL的，所以有些我的语法可能会略微偏离，但从我在手册中读到的内容来看，上面的内容应该是正确的。）