Calling a MySQL query from a shell script after some time interval - mysql

Question

I wanted to execute a MySQL query from a shell script after some time. I have written the script but the output is not as expected. It is printing the same value again from the database. Can someone please help.
SCRIPT- demo.sh
#!/bin/bash
echo "Shell Script to Query a Database!"
echo "--Querying from the Database starts--"
cd "C:\Program Files\MySQL\MySQL Server 5.7\bin"
for i in {1..5};
do
./mysql -u root -proot#123 << EOF
use catalyst_latest;
select id from ci_master limit 1;
EOF
echo "Wait for 2 seconds for the next ID."
sleep 2;
done
echo "--Query Stopped!--"
OUTPUT
$ ./demo.sh
Shell Script to Query a Database!
--Querying from the Database starts--
mysql: [Warning] Using a password on the command line interface can be insecure.
id
282
Wait for 2 seconds for the next ID.
mysql: [Warning] Using a password on the command line interface can be insecure.
id
282
Wait for 2 seconds for the next ID.
mysql: [Warning] Using a password on the command line interface can be insecure.
id
282
Wait for 2 seconds for the next ID.
mysql: [Warning] Using a password on the command line interface can be insecure.
id
282
Wait for 2 seconds for the next ID.
mysql: [Warning] Using a password on the command line interface can be insecure.
id
282
Wait for 2 seconds for the next ID.
--Query Stopped!--
Can you see that 282 getting returned every time? So i want the next ID from the database after 2 seconds. Please tell me how to do it.
Thank you in advance.

Answer 1

You need to remember the returned id value into the bash variable and then reusing that variable in WHERE clause of the query like this:
select id from ci_master where id > $id limit 1
To write output of the command into variable use something like this:
id=$(mysql <options> -Nsqe "<query>")
Option N to skip column names (like id), option s for more silent output, option q for not caching result, option e for the command to execute.
Initially the $id variable should be set to some value like 1 or the minimum of existing values in the table.

Answer 2

#!/bin/bash
echo "Shell Script to Query a Database!"
echo "--Querying from the Database starts--"
cd "C:\Program Files\MySQL\MySQL Server 5.7\bin"
for i in {1..10};
do
temp=`./mysql -u root -proot#123 << EOF
use catalyst_latest;
select id from ci_master limit $i;
EOF`
result=''
for j in $temp
do
result=$j
done
#date;
echo "$result"
echo "Wait for 1 seconds for the next ID."
sleep 1;
done
echo "--Query Stopped!--"