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Only read selected columns
...hs (7 columns) for each year of the data below, for example by using read.table() ?
4 Answers
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How can I join multiple SQL tables using the IDs?
I have 4 different tables that I want to join. The tables are structured with columns as follows:
4 Answers
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How to convert an entire MySQL database characterset and collation to UTF-8?
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Use the ALTER DATABASE and ALTER TABLE commands.
ALTER DATABASE databasename CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;
ALTER TABLE tablename CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;
Or if you're still on MySQL 5.5.2 or older wh...
How can I return pivot table output in MySQL?
If I have a MySQL table looking something like this:
8 Answers
8
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Count number of occurences for each unique value
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Perhaps table is what you are after?
dummyData = rep(c(1,2, 2, 2), 25)
table(dummyData)
# dummyData
# 1 2
# 25 75
## or another presentation of the same data
as.data.frame(table(dummyData))
# dummyData Freq
# 1 1 ...
How can I get column names from a table in Oracle?
...he database to get the column names , not to be confused with data in the table. For example, if I have a table named EVENT_LOG that contains eventID , eventType , eventDesc , and eventTime , then I would want to retrieve those field names from the query and nothing else.
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Hibernate: Automatically creating/updating the db tables based on entity classes
...ts it should be hibernate.hbm2ddl.auto
A value of create will create your tables at sessionFactory creation, and leave them intact.
A value of create-drop will create your tables, and then drop them when you close the sessionFactory.
Perhaps you should set the javax.persistence.Table annotation e...
Define variable to use with IN operator (T-SQL)
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DECLARE @MyList TABLE (Value INT)
INSERT INTO @MyList VALUES (1)
INSERT INTO @MyList VALUES (2)
INSERT INTO @MyList VALUES (3)
INSERT INTO @MyList VALUES (4)
SELECT *
FROM MyTable
WHERE MyColumn IN (SELECT Value FROM @MyList)
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ALTER TABLE without locking the table?
When doing an ALTER TABLE statement in MySQL, the whole table is read-locked (allowing concurrent reads, but prohibiting concurrent writes) for the duration of the statement. If it's a big table, INSERT or UPDATE statements could be blocked for a looooong time. Is there a way to do a "hot alter", li...
How to drop unique in MySQL?
...you can use the following SQL Script to delete the index in MySQL:
alter table fuinfo drop index email;
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