find index in array

1. The concept of arrays An array is a named range that is used to store a series of variable values. Each array element has an associated index (also a keyword) that can be used to access elements. PHP allows you to use numbers or strings evenly

1. Merging Arrays The Array_merge () function merges the arrays together, returning a federated array. The resulting array begins with the first input array parameter and is forced in the order in which the following array parameters appear. In the

basic functions of array manipulationThe key name and value of the arrayArray_values ($arr); Gets the value of the array Array_keys ($arr), gets the key name of the array array_flip ($arr), and the values in the array are exchanged with the key

Basic functions of array manipulationThe key name and value of the arrayArray_values ($arr); Get the value of an arrayArray_keys ($arr); Gets the key name of the arrayArray_flip ($arr); the values in the array are exchanged with the key names (if

The main considerations for designing SQL Server indexes are as follows:Check where condition and join condition column;Use narrow index;Check the selectivity of the column;Check the data type of the column;Consider the order of the columns;Consider

First, the index introductionIn MongoDB, indexes are used to support efficient queries. If there is no index, MONGODB must scan each document in the entire collection to find a matching document. However, if an appropriate index is established,

PHP has a lot of functions about arrays to facilitate array manipulation. Defined: Each entity of an array contains two items: key and value, which can be retrieved by a query key. These keys can be numeric (numerical) or associated (associative)

The main considerations for designing SQL Server indexes are as follows:Check where condition and join condition column;Use narrow index;Check the selectivity of the column;Check the data type of the column;Consider the order of the columns;Consider

Indexes can often greatly improve the efficiency of queries, and if there is no index, MongoDB must scan every file in the collection and select those records that meet the query criteria when reading the data. This scan full set of query efficiency

1. Merging arrays The Array_merge () function merges the arrays together to return an array of unions. The resulting array starts with the first input array parameter, forcing it sequentially in the order in which the array parameters appear later.