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MySQL Articles
Page 347 of 355
How to save MySQL query output to excel or .txt file?
To save MySQL query output into a text file, we can use the OUTFILE command. Let us first create a table. mysql> create table SaveintoTextFile -> ( -> id int, -> name varchar(100) -> ); Query OK, 0 rows affected (0.55 sec) Inserting records into the table. mysql> insert into SaveintoTextFile values(1, 'John'); Query OK, 1 row affected (0.44 sec) mysql> insert into SaveintoTextFile values(101, 'Carol'); Query OK, 1 row affected (0.17 sec) mysql> insert into SaveintoTextFile values(3, 'David'); Query OK, 1 row ...
Read MoreHow to display current connection info in MySQL?
MySQL provides many functions that give the current connection information. For instance, to know about the current user, use the user() function. Syntax mysql> SELECT CURRENT_USER(); Here is the output that displays the name of the current user. +----------------+ | CURRENT_USER() | +----------------+ | root@% | +----------------+ 1 row in set (0.00 sec) In the above, % tells us about localhost. To check the current connection id, use the following method − mysql> SELECT CONNECTION_ID(); The following is the output that shows the current connection id. ...
Read MoreHow to create boolean column in MySQL with false as default value?
To create a column with ‘false’ as the default value, we can use the concept of “default” at the time of creation of the table. Note − 0 represents false and 1 represents true. Creating a table using “default” false. mysql> create table TrueFalseTable -> ( -> Adult boolean default false -> ); Query OK, 0 rows affected (0.65 sec) Inserting records with no value, since we have set “default” above. mysql> insert into TrueFalseTable values(); Query OK, 1 row affected (0.16 sec) To display records. ...
Read MoreHow to use union and order by clause in MySQL?
Union is a type of operator in MySQL. We can use ORDER BY with this to filter records. Use UNION if you want to select rows one after the other from several tables or several sets of rows from a single table all as a single result set. Let us see an example. Creating first table mysql> create table UnionDemo1 -> ( -> id int -> ); Query OK, 0 rows affected (0.59 sec) Inserting records into first table. mysql> insert into UnionDemo1 values(1), (4), (10); Query OK, ...
Read MoreHow to get a list of MySQL views?
To get a list of MySQL views, we can use the SELECT command with LIKE operator. Let us see the syntax first. mysql> SELECT TABLE_SCHEMA, TABLE_NAME -> FROM information_schema.tables -> WHERE TABLE_TYPE LIKE 'VIEW'; The following is the output that displays the total number of views. +--------------+-----------------------------------------------+ | TABLE_SCHEMA | TABLE_NAME | +--------------+-----------------------------------------------+ | sys ...
Read MoreHow to repair MySQL tables from the command line?
The repair of MySQL tables is only applicable to MyISAM engine type, not for InnoDB. Therefore, we need to change the Engine type to MyISAM. The following is an example. Creating a table mysql> create table RepairTableDemo -> ( -> id int, -> name varchar(100) -> ); Query OK, 0 rows affected (0.51 sec) To convert this table to engine type MyISAM, use ALTER. mysql> ALTER TABLE RepairTableDemo ENGINE = MyISAM; Query OK, 0 rows affected (1.14 sec) Records: 0 Duplicates: 0 Warnings: ...
Read MoreHow can I restore the MySQL root user full privileges?
We can restore the MySQL root user full privileges with the help of UPDATE command. Firstly, you need to stop mysqld and restart it with the --skip-grant-tables option. After that, connect to the mysqld server with only mysql (i.e. no -p option, and username may not be required). Issue the below given command in the mysql client to restore the MySQL root user with full privileges. mysql> UPDATE mysql.user SET Grant_priv = 'Y', Super_priv = 'Y' WHERE User = 'root'; Query OK, 0 rows affected (0.04 sec) Rows matched: 1 Changed: 0 Warnings: 0 Above, ...
Read MoreHow to quit/ exit from MySQL stored procedure?
We can quit/ exit from MySQL stored procedure with the help of the LEAVE command. The following is the syntax. Leave yourLabelName; The following is an example. Here, we are creating a new procedure. mysql> delimiter // mysql> CREATE PROCEDURE ExitQuitDemo2(IN Var1 VARCHAR(20)) -> proc_Exit:BEGIN -> IF Var1 IS NULL THEN -> LEAVE proc_Exit; -> END IF; -> END // Query OK, 0 rows affected (0.16 sec) Above, we have set the following LEAVE command to exit from the procedure. If ...
Read MoreMySQL select query to select rows from a table that are not in another table?
For our example, we will create two tables and apply Natural Left Join to get the rows from a table not present in the second table. Creating the first table. mysql> create table FirstTableDemo -> ( -> id int, -> name varchar(100) -> ); Query OK, 0 rows affected (0.48 sec) Inserting records into first table. mysql> insert into FirstTableDemo values(1, 'Bob'), (2, 'John'), (3, 'Carol'); Query OK, 3 rows affected (0.13 sec) Records: 3 Duplicates: 0 Warnings: 0 To display all ...
Read MoreHow to remove all non-alphanumeric characters from a string in MySQL?
Non-alphanumeric characters are as follows − @, !, #, &, (), ?, / There is no inbuilt function to remove non-alphanumeric characters from a string in MySQL. Therefore, we create a function which removes all non-alphanumeric characters. The function declaration and definition is as follows. mysql> delimiter // mysql> CREATE FUNCTION RemoveNonAlphaNumeric( s CHAR(255) ) RETURNS CHAR(255) DETERMINISTIC -> BEGIN -> DECLARE var1, length SMALLINT DEFAULT 1; -> DECLARE result CHAR(255) DEFAULT ''; -> DECLARE ch CHAR(1); ...
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