目標 將 rull欄位值的0.1g*14 粒/1.5mg*30 片/100ml(氨甲環酸0.5g:氯化鈉0.84g)*1 瓶 中的mg/g/ml開頭的數字取出設定到另外一個欄位上去

SELECT id  from sheet2 where rull  like '%ml%' ;

SELECT id,count, LEFT(rull,LOCATE('g',rull)-1)   from sheet2 where rull  like '%g%' ;

SELECT id,count, LEFT(rull,LOCATE('mg',rull)-1)   from sheet2 where rull  like '%mg%' and id not in (SELECT c.id from ( 

SELECT id  from sheet2 where rull  like '%ml%' ) c )

update sheet2 set count=LEFT(rull,LOCATE('mg',rull)-1)    where rull  like '%mg%'  and  id not in (SELECT c.id from ( SELECT id  from sheet2 where rull  like '%ml%' ) c);


update sheet2 set count=LEFT(rull,LOCATE('mg',rull)-1)    where rull  like '%mg%'  and  id not in (SELECT c.id from ( SELECT id  from sheet2 where rull  like '%ml%' ) c);

update sheet2 set count=LEFT(rull,LOCATE('ml',rull)-1)    where rull  like '%ml%' ;

substring_index(str,delim,count)，str是要擷取的字串，delim是擷取的欄位 count是從哪裡開始擷取(為0則是左邊第0個開始，1位左邊開始第一個選取左邊的，-1從右邊第一個開始選取右邊的