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MySQL Cheat Sheet

Here’s a page that’s just too useful not to mirror, some cat named Neal Parikh has a page he calls a MySQL Cheat Sheet; click that link for the latest revision, or read more for my mirrored copy for reference. When I have to do DB work outside of what I usually do day-to-day I hit Google for some tutorials, so having this as a reference will be helpful in the future.

Selecting a database:

<code>mysql> USE database db_name;</code>

Listing databases:

<code>mysql> SHOW DATABASES;</code>

Listing tables in a db:

<code>mysql> SHOW TABLES;</code>

Describing the format of a table:

<code>mysql> DESCRIBE table;</code>

Creating a database:

<code>mysql> CREATE DATABASE db_name;</code>

Creating a table:

<code>mysql> CREATE TABLE table_name (field1_name TYPE(SIZE), field2_name TYPE(SIZE));</code>

Ex: mysql> CREATE TABLE pet (name VARCHAR(20), sex CHAR(1), birth DATE);

Load tab-delimited data into a table:

<code>mysql> LOAD DATA LOCAL INFILE "infile.txt" INTO TABLE table_name;</code>

(Use \n for NULL)

Inserting one row at a time:

<code>mysql> INSERT INTO table_name VALUES ('MyName', 'MyOwner', '2002-08-31');</code>

(Use NULL for NULL)

Retrieving information (general):

<code>mysql> SELECT from_columns FROM table WHERE conditions;
All values: SELECT * FROM table;
Some values: SELECT * FROM table WHERE rec_name = "value";
Multiple critera: SELECT * FROM TABLE WHERE rec1 = "value1" AND rec2 = "value2";</code>

Reloading a new data set into existing table:

<code>mysql> SET AUTOCOMMIT=1; # used for quick recreation of table
mysql> DELETE FROM pet;
mysql> LOAD DATA LOCAL INFILE "infile.txt" INTO TABLE table;</code>

Fixing just one record:

<code>mysql> UPDATE table SET value = "new_value" WHERE record_name = "value";</code>

Selecting specific columns:

<code>mysql> SELECT column_name FROM table;</code>

Retrieving unique output records:

<code>mysql> SELECT DISTINCT column_name FROM table;</code>


<code>mysql> SELECT col1, col2 FROM table ORDER BY col2;
Backwards: SELECT col1, col2 FROM table ORDER BY col2 DESC;</code>

Date calculations:

<code>mysql> SELECT CURRENT_DATE, (YEAR(CURRENT_DATE)-YEAR(date_col)) AS time_diff [FROM table];
MONTH(some_date) extracts the month value and DAYOFMONTH() extracts day.</code>

Pattern Matching:

<code>mysql> SELECT * FROM table WHERE rec LIKE "blah%";</code>

(% is wildcard - arbitrary # of chars) Find 5-char values: SELECT * FROM table WHERE rec like ”_”; (_ is any single character)

Extended Regular Expression Matching:

<code>mysql> SELECT * FROM table WHERE rec RLIKE "^b$";</code>

(. for char, […] for char class, * for 0 or more instances ^ for beginning, {n} for repeat n times, and $ for end) (RLIKE or REGEXP) To force case-sensitivity, use “REGEXP BINARY”

Counting Rows:

<code>mysql> SELECT COUNT(*) FROM table;</code>

Grouping with Counting:

<code>mysql> SELECT owner, COUNT(*) FROM table GROUP BY owner;</code>

(GROUP BY groups together all records for each ‘owner’)

Selecting from multiple tables:

<code>mysql> SELECT pet.name, comment FROM pet, event WHERE pet.name = event.name;</code>

(You can join a table to itself to compare by using ‘AS’)

Currently selected database:

<code>mysql> SELECT DATABASE();</code>

Maximum value:

<code>mysql> SELECT MAX(col_name) AS label FROM table;</code>

Auto-incrementing rows:

<code>mysql> CREATE TABLE table (number INT NOT NULL AUTO_INCREMENT, name CHAR(10) NOT NULL);
mysql> INSERT INTO table (name) VALUES ("tom"),("dick"),("harry");</code>

Adding a column to an already-created table:

<code>mysql> ALTER TABLE tbl ADD COLUMN [column_create syntax] AFTER col_name;</code>

Removing a column:

<code>mysql> ALTER TABLE tbl DROP COLUMN col;</code>

(Full ALTER TABLE syntax available at mysql.com.)

Batch mode (feeding in a script):

<code># mysql -u user -p < batch_file</code>

(Use -t for nice table layout and -vvv for command echoing.) Alternatively:

<code>mysql> source batch_file;</code>