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What is cardinality in MySQL?
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It is an estimate of the number of unique values in the index.
For a table with a single primary key column, the cardinality should normally be equal to the number of rows in the table.
More information.
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A migration to add unique constraint to a combination of columns
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add_index :people, [:firstname, :lastname, :dob], :unique => true
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How to implement a unique index on two columns in rails
I have a table and I'm trying to add a unique index on two columns. Those columns are also indexed. So my question is if I just can remove the indexes who were just for one column or if I have to use all three indexes:
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How can I declare and define multiple variables in one line using C++?
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int column = 0, row = 0, index = 0;
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Does order of where clauses matter in SQL?
...PLE having 3 columns ID, LastName, FirstName , none of these columns are indexed.
LastName is more unique, and FirstName is less unique.
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Java ArrayList replace at specific index
...reated an ArrayList of bulbs, and I'm trying to replace a bulb at specific index with another bulb. So with the following heading, how do I proceed?
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How to search for a part of a word with ElasticSearch
...use standard tokenizer and nGram just as a filter. Here is my setup:
{
"index": {
"index": "my_idx",
"type": "my_type",
"analysis": {
"index_analyzer": {
"my_index_analyzer": {
"type": "custom",
"tokenizer": "standard",
"filter": [
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Is there a foreach loop in Go?
...g iteration
variables and then executes the block.
As an example:
for index, element := range someSlice {
// index is the index where we are
// element is the element from someSlice for where we are
}
If you don't care about the index, you can use _:
for _, element := range someSlice...
Get child node index
...tensions such as jQuery, etc.), is there a way to determine a child node's index inside of its parent node without iterating over and comparing all children nodes?
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Using wget to recursively fetch a directory with arbitrary files in it
...-recursive, of course), otherwise it will follow the link in the directory index on my site to the parent directory. So the command would look like this:
wget --recursive --no-parent http://example.com/configs/.vim/
To avoid downloading the auto-generated index.html files, use the -R/--reject opt...