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Simulate CREATE DATABASE IF NOT EXISTS for PostgreSQL?
...k around it from within psql by executing the DDL statement conditionally:
SELECT 'CREATE DATABASE mydb'
WHERE NOT EXISTS (SELECT FROM pg_database WHERE datname = 'mydb')\gexec
The manual:
\gexec
Sends the current query buffer to the server, then treats each column of each row of the query's outpu...
Retrieve the maximum length of a VARCHAR column in SQL Server
...
Use the built-in functions for length and max on the description column:
SELECT MAX(LEN(DESC)) FROM table_name;
Note that if your table is very large, there can be performance issues.
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Difference between string object and string literal [duplicate]
...fference. s1 will refer to an interned String object. This means, that the character sequence "abcde" will be stored at a central place, and whenever the same literal "abcde" is used again, the JVM will not create a new String object but use the reference of the cached String.
s2 is guranteed to be...
How to get the sizes of the tables of a MySQL database?
...he size of a table (although you need to substitute the variables first):
SELECT
table_name AS `Table`,
round(((data_length + index_length) / 1024 / 1024), 2) `Size in MB`
FROM information_schema.TABLES
WHERE table_schema = "$DB_NAME"
AND table_name = "$TABLE_NAME";
or this query ...
Qt 5.1.1: Application failed to start because platform plugin “windows” is missing
...e main method before the QApplication call like this:
int main( int argc, char *argv[] )
{
QCoreApplication::addLibraryPath(".");
QApplication app( argc, argv );
...
return app.exec();
}
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Is there a better way to dynamically build an SQL WHERE clause than by using 1=1 at its beginning?
... {2}", clause, appender, condition);
}
Use it like this
string query = "SELECT * FROM Table1 {0}";
string whereClause = string.Empty;
if (condition 1)
whereClause = AddCondition(whereClause, "AND", "Col=1");
if (condition 2)
whereClause = AddCondition(whereClause, "AND", "Col2=2");
str...
Why is 128==128 false but 127==127 is true when comparing Integer wrappers in Java?
...the JLS (5.1.7).
If the value p being boxed is true, false, a byte, a char in the range \u0000 to \u007f, or an int or short number between -128 and
127, then let r1 and r2 be the results of any two boxing conversions
of p. It is always the case that r1 == r2.
A simple rule to remember wh...
Multiple line code example in Javadoc comment
...se of Eclipse, this is because of (bugged?) javadoc utility. If you have @ character in the multiline code inside {@code ...multiline...} then javadoc fails to parse it correctly:( At least this is what I see with Oracle JDK1.7.0_45 javadoc implementation.
– Male
...
SQLite - How do you join tables from different databases?
...s with keyword
.databases
Then you should be able to do the following.
select
*
from
db1.SomeTable a
inner join
db2.SomeTable b on b.SomeColumn = a.SomeColumn;
Note that "[t]he database names main and temp are reserved for the primary database and database to hold temporary tables a...
Filter dataframe rows if value in column is in a set list of values [duplicate]
...id 7
9 1980-01-10 9 Jones 4
There are multiple ways of selecting or slicing the data.
Using .isin
The most obvious is the .isin feature. You can create a mask that gives you a series of True/False statements, which can be applied to a dataframe like this:
mask = df['STK_ID'].isin...