大约有 47,000 项符合查询结果(耗时:0.0203秒) [XML]

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What's faster, SELECT DISTINCT or GROUP BY in MySQL?

...'t, then use DISTINCT. GROUP BY in MySQL sorts results. You can even do: SELECT u.profession FROM users u GROUP BY u.profession DESC and get your professions sorted in DESC order. DISTINCT creates a temporary table and uses it for storing duplicates. GROUP BY does the same, but sortes the disti...
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How to concatenate columns in a Postgres SELECT?

... an explicit coercion to text [...] Bold emphasis mine. The 2nd example (select a||', '||b from foo) works for any data types since the untyped string literal ', ' defaults to type text making the whole expression valid in any case. For non-string data types, you can "fix" the 1st statement by c...
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SQL - using alias in Group By

... following order: FROM clause WHERE clause GROUP BY clause HAVING clause SELECT clause ORDER BY clause For most relational database systems, this order explains which names (columns or aliases) are valid because they must have been introduced in a previous step. So in Oracle and SQL Server, you...
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MySQL case insensitive select

Can anyone tell me if a MySQL SELECT query is case sensitive or case insensitive by default? And if not, what query would I have to send so that I can do something like: ...
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Firefox ignores option selected=“selected”

If you change a dropdown and refresh the page, Firefox seems to ignore the selected attribute. 20 Answers ...
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How do I bind to list of checkbox values with AngularJS?

...repeat="fruitName in fruits"> <input type="checkbox" name="selectedFruits[]" value="{{fruitName}}" ng-checked="selection.indexOf(fruitName) > -1" ng-click="toggleSelection(fruitName)" > {{fruitName}} </label> And the appropriate controller code would be: ...
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Function to Calculate Median in SQL Server

... in all cases. It also requires SQL 2012 or later. DECLARE @c BIGINT = (SELECT COUNT(*) FROM dbo.EvenRows); SELECT AVG(1.0 * val) FROM ( SELECT val FROM dbo.EvenRows ORDER BY val OFFSET (@c - 1) / 2 ROWS FETCH NEXT 1 + (1 - @c % 2) ROWS ONLY ) AS x; Of course, just because o...
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this.setState isn't merging states as I would expect

...do recursive merge. You can use the value of the current state this.state.selected to construct a new state and then call setState() on that: var newSelected = _.extend({}, this.state.selected); newSelected.name = 'Barfoo'; this.setState({ selected: newSelected }); I've used function _.extend() ...
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Adding options to a using jQuery?

... This did NOT work in IE8 (yet did in FF): $("#selectList").append(new Option("option text", "value")); This DID work: var o = new Option("option text", "value"); /// jquerify the DOM object 'o' so we can use the html method $(o).html("option text"); $("#selectList").a...
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Regex select all text between tags

What is the best way to select all the text between 2 tags - ex: the text between all the 'pre' tags on the page. 17 Answe...