[Development/SQL - SQL command (UPDATE statement)]
3.04
Regardless of the table definition, choose two statements that always result in an error.
-
DELETE FROM t1. Table1 t 2 WHERE a = b;
-
DELETE table1 WHERE column 1 = 100;
- DELETE FROM table1 t1, table2 t2 WHERE t1. A = t 2. B;
- DELETE FROM table1;
- DELETE FROM table1 WHERE a IN (SELECT x FROM table2);
[Development/SQL - SQL command (data type)]
3.03
Choose the correct statement about PostgreSQLs
data types.
- Since INTEGER can handle integers up to 10 digits, declaring it as NUMERIC (10) is the same.
- Since REAL can handle decimal numbers with precision of 6 digits, declaring it as NUMERIC (10, 6) is the same.
- DOUBLE PRECISION can handle decimal numbers with a precision of 15 digits, so declaring it as NUMERIC (10, 15) is the same.
- Since INTEGER's operation is faster than NUMERIC, if the value is always an integer, you should use INTEGER instead of NUMERIC.
- It is not possible to expect that the result will be true when performing equivalence comparison (comparison of the form of a = b) for 0.1 of the REAL type and 0.1 of the NUMERIC type.
[Development/SQL - SQL command (table definition)]
3.02
Choose the correct way to create a table with the id
column as the primary key.
- CREATE TABLE test (PRIMARY KEY id INTEGER, value TEXT);
- CREATE TABLE test (id INTEGER PRIMARY KEY, value TEXT);
-
CREATE TABLE test (id INTEGER, value TEXT, PRIMARY KEY = id);
-
CREATE TABLE test (id INTEGER, value TEXT, PRIMARY KEY id);
-
CREATE TABLE test (id INTEGER, value TEXT, PRIMARY KEY (id));
[Development/SQL - Built-in functions
(aggregate functions)]
3.01
A table is created and data is inserted using the
following sequence of SQL statements.
CREATE TABLE sample1 (val INTEGER);
INSERT INTO sample1 (val) VALUES (1), (2), (3), (4), (NULL);
The following SELECT statement is executed.
SELECT count(*), count(val), avg(val) FROM sample1;
Which of the following is the correct combination of returned values?
- 5, 5, 2
- 5, 4, 2
-
5, 4, 2.5
-
4, 4, 2.5
-
5, 4, NULL
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