Problem children are coming from the different World OVA PHP interview encountered problems here do the next record

Code optimization

Copy the Code code as follows:

for ($i =0; $i <8; $i + +) {
Array_push ($week, $arr);
}

Copy the Code code as follows:

for ($i =0; $i <8; $i + +) {
$week []= $arr [$i];
}
So there's no extra burden on the calling function.

The advantages and disadvantages of building an index
Benefit: The query will first go to the number of rows in the index list to target a specific value at a time, greatly reducing the number of rows to be traversed
Cons: In any case to query this table, field a large number of duplicate values, to increase the index does not make any sense
Record less, increase the index does not bring speed optimization instead of wasting storage space, because the index is required storage space, and a fatal disadvantage is that for each execution of Update|insert|delete, the index of the field must recalculate the update

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