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- The difference between date and timestamp in oracle
- DATE in Oracle stores only the date part, accurate to days, while TIMESTAMP stores date and time parts, accurate to microseconds, and can store time zone offsets. They also differ in storage space, scope and format. Best practice is to choose the appropriate type based on the information you need to store: use DATE if you need only date information, or TIMESTAMP if you need precise time and time zone information.
- Oracle 960 2024-05-02 23:30:26
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- What is rownum in oracle
- ROWNUM in Oracle is a pseudo column that represents the row sequence number in the current query result. It is mainly used for paging queries, row number display and avoiding duplicate data.
- Oracle 1278 2024-05-02 23:27:53
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- How to arrange in reverse order in oracle
- In Oracle, reverse sorting can be achieved through the ORDER BY clause: use the ORDER BY column_name DESC syntax, where column_name is the name of the column to be sorted. For example: SELECT first_name, last_name FROM employees ORDER BY last_name DESC.
- Oracle 1118 2024-05-02 23:24:52
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- Decimal usage in oracle
- The Oracle DECIMAL data type provides high-precision storage of decimal values for calculations that require precision. Features include: Configurable precision, variable length between 1 and 38, based on precision and range High precision, accurate calculations of currencies, scientific data, etc. Immutable, values cannot be changed after they are created
- Oracle 1086 2024-05-02 23:24:37
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- How to use unique in oracle
- The UNIQUE constraint in Oracle ensures that a specific column or combination of columns in the table has a unique value, preventing duplicate data insertion. It is implemented through the following rules: 1. In an insert or update operation, the value of a specified column or column combination cannot be repeated with an existing value; 2. Indexes are allowed to be created to improve query efficiency.
- Oracle 1082 2024-05-02 23:24:17
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- and usage in oracle
- The AND operator is used to combine conditions in Oracle and returns TRUE if all conditions are TRUE and FALSE otherwise. Usage includes: Combining simple conditions Nested conditions to create complex conditions Combined with the NOT operator to create negative conditions Have higher precedence than the OR operator
- Oracle 1063 2024-05-02 23:22:00
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- Usage of any and all in oracle
- ANY and ALL are operators used in Oracle for conditional checking of set elements. ANY checks whether any element in the set satisfies the condition, ALL checks whether all elements satisfy the condition. ANY is often used to find any item that satisfies a condition, while ALL is used to verify that all items satisfy the condition.
- Oracle 1023 2024-05-02 23:21:37
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- What does union mean in oracle?
- UNION is a data manipulation language command that vertically combines the results of two or more SELECT statements but retains only unique rows. It requires that the result sets of the merged SELECT statements have the same number of columns and data types, and can only handle compatible data types (for example, you cannot combine numeric columns with string columns).
- Oracle 1171 2024-05-02 23:21:17
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- Alternative way of writing union in oracle
- Alternatives to UNION in Oracle include: Direct addition (+): joins query results, retaining duplicate rows. UNION ALL: Join query results, retaining all rows. WITH subquery: Create a temporary table, contain the query results, and then query the temporary table. CTE: Define temporary tables or views for subsequent queries. SQL JOIN: Join related rows in multiple tables.
- Oracle 574 2024-05-02 23:18:50
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- How to use replace function in oracle
- The REPLACE function in Oracle is used to replace a specified substring in a string with another substring. The methods of use include: 1. Replace errors or spelling errors in the text; 2. Change the content of the string; 3. From characters Remove a specific substring from a string.
- Oracle 1230 2024-05-02 23:18:32
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- How to use convert function in oracle
- The CONVERT function converts a value in Oracle from one data type to another, and its syntax is CONVERT(<result data type>, <input value>). It can be used to convert string to number, number to string, date to string, string to date, binary to string and string to binary.
- Oracle 670 2024-05-02 23:18:18
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- What does nvl mean in oracle
- The NVL function in Oracle is used to handle null values, it checks if expr1 is null and returns expr2 if it is null, otherwise it returns expr1. Advantages include preventing errors, returning user-friendly values, and simplifying queries. The limitation is that it can only handle a single value and the replacement value must be compatible with expr1's data type.
- Oracle 1271 2024-05-02 23:15:48
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- How to use ifnull in oracle
- The Oracle IFNULL function is used to return a default value when a specified column or expression is NULL. Its uses include: replacing NULL values to prevent errors. Missing data were imputed for data analysis. Convert NULL values to specific values to improve readability.
- Oracle 753 2024-05-02 23:15:31
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- usage of distinct in oracle
- The DISTINCT operator removes duplicate rows from a result set and can be used to extract unique values or eliminate duplicate rows in join results. It can be applied to a single table, use multiple tables to eliminate duplicate rows, or use multiple columns as parameters. DISTINCT may affect query performance because it does not utilize indexes and may increase processing time.
- Oracle 606 2024-05-02 23:12:56
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- Concat usage in oracle
- The CONCAT function in Oracle is used to concatenate multiple strings into one. The usage is CONCAT(string1, string2, ...). The input is multiple strings and the output is the new string after concatenation. It supports NULL value handling and automatic string conversion to insert text using delimiters. However, it is recommended to use the DBMS_LOB.APPEND or STRINGAGG function to optimize performance when connecting to a large number of connections.
- Oracle 1062 2024-05-02 23:12:38
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