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How to change a nullable column to not nullable in a Rails migration?
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This causes problems when the table already has null values. See my answer
– Rick Smith
Aug 8 '14 at 20:27
5
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How do I generate random number for each row in a TSQL Select?
I need a different random number for each row in my table. The following seemingly obvious code uses the same random value for each row.
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How do I check if a column is empty or null in MySQL?
I have a column in a table which might contain null or empty values. How do I check if a column is empty or null in the rows present in a table?
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Which @NotNull Java annotation should I use?
...nt approaches. Some packages use JLS 9.6.4.1 style contexts. The following table gives an overview:
FIELD METHOD PARAMETER LOCAL_VARIABLE
android.support.annotation X X X
edu.umd.cs.findbugs.annotations X X X X
org.jetbra...
JPA EntityManager: Why use persist() over merge()?
...nate Session (a.k.a Persistence Context) and is not mapped to any database table row is considered to be in the New (Transient) state.
To become persisted we need to either explicitly call the EntityManager#persist method or make use of the transitive persistence mechanism.
Persistent (Managed)
A...
Should try…catch go inside or outside a loop?
...ch structures are placed. Internally, they are implemented as a code-range table in a structure that is created when the method is called. While the method is executing, the try/catch structures are completely out of the picture unless a throw occurs, then the location of the error is compared again...
How do I retrieve an HTML element's actual width and height?
...r browsers use this:
<style type="text/css">
html,body {display:table; height:100%;width:100%;margin:0;padding:0;}
body {display:table-cell; vertical-align:middle;}
div {display:table; margin:0 auto; background:red;}
</style>
<body><div>test<br>test</div...
SET NAMES utf8 in MySQL?
...ters to show on websites properly when the data was queried from MySQL. My tables and columns are set to UTF-8 in MySQL—so should this be necessary?
– NexusRex
Aug 30 '11 at 19:15
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Omit rows containing specific column of NA
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It is possible to use na.omit for data.table:
na.omit(data, cols = c("x", "z"))
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JSTL in JSF2 Facelets… makes sense?
...item} is only available during view render time. Same is true for an h:dataTable and similar components.
<c:if>/<c:choose> vs rendered
As another example, this Facelets markup conditionally adding different tags using <c:if> (you can also use <c:choose><c:when><c:o...