The Surname column is indexed. WHERE Surname LIKE 'Uwi%' is fast, but WHERE Surname LIKE '%mana' scans the whole table. Why?
La colonne Surname est indexée. WHERE Surname LIKE 'Uwi%' est rapide, mais WHERE Surname LIKE '%mana' parcourt toute la table. Pourquoi ?
Answers
AThe second query needs a password before it can use the indexLa seconde requête a besoin d'un mot de passe avant de pouvoir utiliser l'index
BA normal index is sorted from the start; a leading % gives no startUn index normal est trié depuis le début ; un % initial ne donne aucun point de départ
CLIKE never uses indexes under any circumstancesLIKE n'utilise jamais d'index, en aucun cas
DThe database is out of memoryLa base manque de mémoire
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