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- How to replace rownum in oracle
- In addition to Oracle's ROWNUM pseudo-column, you can obtain the sequence number of a row using the following alternatives: 1. Subquery (using nested subqueries); 2. Analytical functions (such as ROW_NUMBER()); 3. Sequence (for new inserts rows); 4. Temporary table (store row numbers by creating a temporary table).
- Oracle 629 2024-05-03 00:18:32
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- What function is the same as the count function in Oracle?
- The COUNT function in Oracle is equivalent to the COUNT() function in SQL. It is used to count the number of non-null values in a specified column or expression, including: COUNT(*): Counts the number of all non-null values in the table. COUNT(column_name): Count the number of non-null values in the specified column. COUNT(DISTINCT column_name): Counts the number of unique non-null values in the specified column.
- Oracle 829 2024-05-03 00:15:43
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- Usage of listagg function in oracle
- The LISTAGG function concatenates a set of rows of data into a string, using the specified concatenation character to separate elements. Usage includes: 1. Join all values in a column; 2. Separate values using join characters; 3. Ignore NULL values; 4. Partition by group; 5. Join values sequentially.
- Oracle 460 2024-05-03 00:15:28
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- Are null and empty string equivalent in Oracle?
- In Oracle, NULL and empty string are not equal. NULL represents an unknown value and is not equal to any value; an empty string is a string of length 0 that can be equal to other empty strings. The difference between NULL and the empty string is that NULL cannot be used in arithmetic operations or concatenation operations, while the empty string can.
- Oracle 448 2024-05-03 00:12:52
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- Usage of regexplike in oracle
- The Oracle REGEXP_LIKE operator is used to perform regular expression matching, check whether a string matches the specified pattern, and return a Boolean value. It supports various metacharacters such as ., *, +, ?, ^, $, [], {}, allowing complex matching patterns. Additionally, it has optional options like match_parameter (match case/multiple lines) and encoding (character encoding).
- Oracle 515 2024-05-03 00:09:51
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- Usage of regexp_like in oracle
- The REGEXP_LIKE function in Oracle is used to compare whether a string matches a regular expression and returns a Boolean value: Syntax: REGEXP_LIKE(string, regexp, [condition]) Parameters: String, regular expression pattern, optional matching condition ( Default: simple comparison) Usage: Specify strings and regular expression patterns, such as REGEXP_LIKE('string', 'pattern') Example: Match starting with "ABC", containing "XYZ" or case-insensitively matching "PATTERN" string
- Oracle 405 2024-05-03 00:09:33
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- What is the function that intercepts from right to left in Oracle?
- Oracle's LTRIM function is used to truncate all whitespace characters from the right side of a string, including spaces, tabs, newlines, and carriage returns. It returns the trimmed string, or the original string if the string does not contain whitespace.
- Oracle 854 2024-05-03 00:09:15
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- How to use tochar in oracle
- The Oracle TO_CHAR function converts a number, date, or time value to a string. The format string specifies the output format, including date, time, and number format elements. Common date format elements include "%Y" (year) and "%m" (month), and number format elements include "9" (number) and "." (decimal point). For example: Convert date to "YYYY-MM-DD": SELECT TO_CHAR(sysdate, 'YYYY-MM-DD') FROM dual;
- Oracle 919 2024-05-03 00:06:58
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- How to use explain in oracle
- The EXPLAIN command in Oracle is used to analyze the execution plan of a SQL statement. The method of use is to add the EXPLAIN keyword before the SQL statement. EXPLAIN results contain information such as ID, operator type, row count estimate, cost estimate, output row count estimate, access predicates, and filter predicates, which can be used to optimize query performance, identify costly operators, and tables that may benefit from optimization techniques.
- Oracle 623 2024-05-03 00:06:39
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- Can date type fields in Oracle be empty characters?
- No, DATE type fields in Oracle do not allow null characters; it enforces a valid date value, and null date values are interpreted as NULL.
- Oracle 709 2024-05-03 00:03:48
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- Can the date type in oracle be empty?
- Can DATE type be null in Oracle? Yes, you can use NULL values to represent empty date values.
- Oracle 821 2024-05-03 00:03:34
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- How to enter date type in oracle
- There are three ways to enter the DATE type in Oracle: direct input, using the TO_DATE function, and using the CAST function. Direct input must follow the YYYY-MM-DD HH24:MI:SS format; the TO_DATE function syntax is TO_DATE(string, formatted string); the CAST function syntax is CAST(string AS DATE).
- Oracle 866 2024-05-03 00:03:16
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- What is the job in oracle for?
- Jobs in Oracle are predefined tasks that are automatically executed at a specified time, such as triggering operations, sending notifications, calling programs, and maintaining data. When creating a Job, you need to define the name, schedule, actions, and status, and use ENABLE or DISABLE to control the activity status. Job benefits include automating tasks, scheduling tasks, parallel processing, and monitoring and control through tools.
- Oracle 375 2024-05-03 00:01:09
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- What is the difference between nvl in oracle and nvl in hive
- Oracle and Hive's NVL functions are used to handle NULL values, but there are differences: NULL handling: Hive NVL can handle NULL replacement_value, while Oracle NVL cannot. Nested NULL checks: Hive NVL can check for NULL in nested expressions, while Oracle NVL cannot.
- Oracle 1100 2024-05-03 00:00:49
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- substr usage in oracle
- The SUBSTR function in Oracle extracts a specific number of characters from a string. The syntax is SUBSTR(string, start_position, length), where string is the target string, start_position is the starting extraction position (starting from 1), and length is the number of characters extracted. A negative starting position means counting down from the end of the string, and omitting the length parameter extracts all characters from the starting position to the end of the string.
- Oracle 950 2024-05-03 00:00:31
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