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What's the difference between VARCHAR and CHAR?
...: when Anon. says "your content is a fixed size" it means the rows of your table must contain all fixed size fields. You get no performance improvement if you use CHAR against VARCHAR in one field, but the table contains other fields that are VARCHAR.
– Marco Demaio
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postgresql COUNT(DISTINCT …) very slow
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You can use this:
SELECT COUNT(*) FROM (SELECT DISTINCT column_name FROM table_name) AS temp;
This is much faster than:
COUNT(DISTINCT column_name)
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Row count with PDO
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$sql = "SELECT count(*) FROM `table` WHERE foo = ?";
$result = $con->prepare($sql);
$result->execute([$bar]);
$number_of_rows = $result->fetchColumn();
Not the most elegant way to do it, plus it involves an extra query.
PDO has PDOStatemen...
Is it possible to force Excel recognize UTF-8 CSV files automatically?
...nsion XLS you will get the correct result.
Content of UTF8 XLS file:
<table>
<tr><td>Colum1</td><td>Column2</td></tr>
<tr><td>Val1</td><td>Val2</td></tr>
<tr><td>Авиабилет</td><td>Tλλη...
Why should I use document based database instead of relational database?
...ds of applications or domains where the document based database is more suitable than the relational database?
7 Answers
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SQLite string contains other string query
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Using LIKE:
SELECT *
FROM TABLE
WHERE column LIKE '%cats%' --case-insensitive
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SQL Server: Get data for only the past year
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This will have very bad performance on big tables, you query will loop over every record to evaluate the year value of the date, it would be better to use a date range
– Adriaan Davel
May 30 '12 at 15:43
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What is the difference between single and double quotes in SQL?
...stant or a date/time constant.
Double quotes delimit identifiers for e.g. table names or column names. This is generally only necessary when your identifier doesn't fit the rules for simple identifiers.
See also:
Do different databases use different name quote?
You can make MySQL use double-q...
How to select distinct rows in a datatable and store into an array
I have a dataset objds. objds contains a table named Table1. Table1 contains column named ProcessName. This ProcessName contains repeated names.So i want to select only distinct names.Is this possible.
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Create an empty data.frame
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You could use read.table with an empty string for the input text as follows:
colClasses = c("Date", "character", "character")
col.names = c("Date", "File", "User")
df <- read.table(text = "",
colClasses = colClasses,
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