minte9
SoftwareDevelopment / MYSQL





GROUP_CONCAT 

 
SELECT GROUP_CONCAT(ancestor) AS ancestors FROM catg_path WHERE descendant=7 
//ancestor: 2,5,7

SELECT GROUP_CONCAT(ancestor SEPARATOR ' / ') AS ancestors FROM catg_path WHERE descendant=7
//ancestors: 2 / 5 / 7

SELECT GROUP_CONCAT(ancestor ORDER BY ancestor DESC SEPARATOR ' / ') AS ancestors 
            FROM catg_path WHERE descendant=7 
//ancestors: 7 / 5 / 2

CONCAT_WS 

 
SELECT CONCAT_WS(" / ", catg, subcatg) FROM catg WHERE catg='programming'; // jQuery / MySQL / PHP

CONCAT 

 
// returns NULL if any argument is NULL

SELECT CONCAT('My', 'S', 'QL'); 

// Output: 'MySQL'






Questions and answers:
Clink on Option to Answer




1. How do you serialize field values?

  • a) SELECT {{GROUP_CONCAT(catg)}} FROM catgs
  • b) SELECT {{CONCAT_WS(catg)}} FROM catgs

2. How do you concat multiple fields?

  • a) SELECT {{CONCAT}}(catg, subcatg, " / ") FROM subcatgs


References: