Uly.me

cloud engineer

MySQL Select Like

Here’s how to perform SQL searches using the like operator.

# Format
SELECT column1, column2 FROM table_name WHERE column LIKE pattern;
# Search for an entry starting with a 'joe.'
SELECT id,username,address FROM users WHERE username LIKE 'joe%';
# Search for an entry ending with a 'joe.' 
SELECT id,username,address FROM users WHERE username LIKE '%joe';
# Search for any entry with 'joe' from any position. 
SELECT id,username,address FROM users WHERE username LIKE '%joe%';
# Finally, using "_" as wildcards. Find any field with "j" in the second position.
SELECT id,username,address FROM users WHERE username LIKE '_j';

MySQL Read Only

If you need to perform backup or replicate a database, you can lock up the database by doing a global read block to make it read-only.

The process is:

  1. Make the server read-only, so that it processes only retrievals and blocks updates.
  2. You can then perform the backup.
  3. Change the server back to its normal read/write state.

Read only.

FLUSH TABLES WITH READ LOCK;
SET GLOBAL read_only = ON;

Back to normal mode.

SET GLOBAL read_only = OFF;
UNLOCK TABLES;

You can run these MySQL commands within MySQL or via a bash terminal. Check out my previous post.

Running MySQL commands from the Terminal

You can run MySQL commands from the terminal by using -e switch. Here are a few examples.

mysql -u username -p -e "create database mydb"
mysql -u username -p -e "use mydb"
mysql -u username -p database -e "select * from mytable"

If you have .mycnf configured, you can omit the username and password.

mysql -e "create database mydb"
mysql -e "use mydb"
mysql -e "select * from mytable"

To run multiple commands from a single line, separate the commands using a semicolon.

mysql -e "create database somedb; use mydb; select * from mytable;"