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How can I add comments in MySQL?
...es of commenting are supported
Hash base single line commenting using #
Select * from users ; # this will list users
Double Dash commenting using --
Select * from users ; -- this will list users
Note : Its important to have single white space just after --
3) Multi line commenting using ...
MySQL: Selecting multiple fields into multiple variables in a stored procedure
Can I SELECT multiple columns into multiple variables within the same select query in MySQL?
3 Answers
...
CROSS JOIN vs INNER JOIN in SQL
...ame situation.
These 2 examples will return the same result:
Cross join
select * from table1 cross join table2 where table1.id = table2.fk_id
Inner join
select * from table1 join table2 on table1.id = table2.fk_id
Use the last method
...
Bash if statement with multiple conditions throws an error
...ration by reading an entrypoint.sh script written by the contributors from MySQL that checks whether the specified variables were set.
As the script shows, you can pipe them with -a, e.g.:
if [ -z "$MYSQL_ROOT_PASSWORD" -a -z "$MYSQL_ALLOW_EMPTY_PASSWORD" -a -z "$MYSQL_RANDOM_ROOT_PASSWORD" ]; the...
Increment value in mysql update query
...ion to numbers.
To demonstrate, the following will produce the result 6:
SELECT ' 05.05 '+'.95';
String concatenation in MySQL requires the CONCAT() function so there is no ambiguity here and MySQL converts the strings to floats and adds them together.
I actually think the reason the initial q...
Change auto increment starting number?
...foobar(moobar) values ("def");
INSERT INTO foobar(moobar) values ("xyz");
select * from foobar;
'10', 'abc'
'11', 'def'
'12', 'xyz'
This auto increments the id column by one starting at 10.
Auto increment in MySQL by 5, starting at 10:
drop table foobar
create table foobar(
id IN...
Datetime equal or greater than today in MySQL
...
SELECT * FROM users WHERE created >= CURDATE();
But I think you mean created < today
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improve this answer
...
SQL statement to get column type
...
Using SQL Server:
SELECT DATA_TYPE
FROM INFORMATION_SCHEMA.COLUMNS
WHERE
TABLE_NAME = 'yourTableName' AND
COLUMN_NAME = 'yourColumnName'
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UPDATE multiple tables in MySQL using LEFT JOIN
...= t1.id
SET t1.col1 = newvalue
WHERE t2.id IS NULL
Note that for a SELECT it would be more efficient to use NOT IN / NOT EXISTS syntax:
SELECT t1.*
FROM t1
WHERE t1.id NOT IN
(
SELECT id
FROM t2
)
See the article in my blog for performance details...
SQL Server indexes - ascending or descending, what difference does it make?
...TE INDEX ix_index ON mytable (col1, col2 DESC);
can be used for either:
SELECT *
FROM mytable
ORDER BY
col1, col2 DESC
or:
SELECT *
FROM mytable
ORDER BY
col1 DESC, col2
, but not for:
SELECT *
FROM mytable
ORDER BY
col1, col2
An index on a single colum...