Introducing MySQL SQL 41 This SELECT command tells (Budget web hosting)
Introducing MySQL SQL 41 This SELECT command tells the database to pull all columns, using the * character, from the acc table. The database responds with a table using a heading with the column names found in the database used when we first defined the table. Next, all of the data from the table is placed in the output table and displayed accordingly. Now we can limit the columns of data with our SELECT: mysql> SELECT acc_id, username FROM acc; +———+———–+ | acc_id | username | +———+———–+ | 1034033 | jsmith | | 1034055 | jdoe | | 1034067 | jthompson | | 1034089 | sstanford | | 1034123 | blewis | | 1034154 | ysheets | | 1034034 | jime | | 1034546 | jjmyers | +———+———–+ 8 rows in set (0.00 sec) In this example, we have specifically listed the columns we wish to pull data from and at the same time requested all of the data. The system will output the data in the familiar table format. The same query will be used, but a condition is placed on the data we wish to pull. mysql> SELECT acc_id, username FROM acc WHERE username = ‘jime’; +———+———-+ | acc_id | username | +———+———-+ | 1034034 | jime | +———+———-+ 1 row in set (0.00 sec) The same query is used here, but a WHERE clause limits the data to be pulled based on the actual value found in the username field. The condition with the SELECT query can hold logical operators to further refine the selection criteria. For example: mysql> SELECT * FROM acc WHERE password IS NULL AND username = ‘jime’; +———+———-+———-+—————-+ | acc_id | username | password | ts | +———+———-+———-+—————-+ | 1034034 | jime | NULL | 20021014112415 | +———+———-+———-+—————-+ 1 row in set (0.00 sec)
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