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- regr_count usage in oracle
- The REGEXP_COUNT function counts the number of matches of a specific regular expression in a string. It receives two parameters: string and pattern, and returns the number of matches. If there is no match, 0 is returned. Other uses include checking for a match, extracting subgroups of a match, and replacing matches using the REPLACE() function.
- Oracle 1122 2024-04-30 07:42:13
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- How to use count function in oracle
- The COUNT function in Oracle is used to count non-null values in a specified column or expression. The syntax is COUNT(DISTINCT <column_name>) or COUNT(*), which counts the number of unique values and all non-null values respectively.
- Oracle 826 2024-04-30 07:39:13
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- How to use coalesce function in oracle
- The Oracle COALESCE function returns the first non-null value in a set of expressions and is commonly used in data processing and repairing missing values. Usage: 1. Determine the expression to be checked; 2. Specify the COALESCE function; 3. Provide the expression to be checked. This function accepts any number of expressions as parameters and returns the first non-null value, or NULL if all expressions are null.
- Oracle 1043 2024-04-30 07:36:15
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- How to delete table in oracle
- To delete an Oracle table, perform the following steps: 1. Connect to the database; 2. Execute the DROP TABLE command and specify the table name; Note: Deleting a table will permanently delete its data. Please ensure that the table is no longer needed and update the table that depends on it. database object.
- Oracle 413 2024-04-30 07:33:11
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- The difference between blob and clob in oracle
- The main differences between BLOB (Binary Large Object) and CLOB (Character Large Object) in Oracle are: 1. BLOB stores binary data, while CLOB stores character data; 2. The maximum size of BLOB is 4 GB, and the maximum size of CLOB is 4 GB or database block 32 times the size; 3. BLOB does not support indexes, while CLOB supports part of the index; 4. Querying BLOB will load the entire BLOB, while querying CLOB only loads the first 4000 characters; 5. BLOB is stored in the LOB segment, while CLOB
- Oracle 431 2024-04-30 07:30:26
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- Usage of substr in oracle
- The SUBSTR function is used to extract a substring from a string. The syntax is SUBSTR(string, start, length). You need to specify the source string, starting position and length (optional), and the function extracts the substring of the specified length starting from the specified position. For example, SUBSTR('Hello World', 1, 5) returns "Hello" and SUBSTR('Hello World', 7) returns "World".
- Oracle 431 2024-04-30 07:24:16
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- date usage in oracle
- The DATE data type stores date values that do not contain time information. Its uses include saving date information, date operations, and data type conversion. Example usages include: calculating date intervals, comparing dates, and extracting date components. Note that the DATE type does not store time zone information, which ranges from January 1, 4712 BC to December 31, 9999 AD.
- Oracle 1084 2024-04-30 07:21:15
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- The difference between inner join and outer join in oracle
- The connection types in Oracle are divided into inner joins and outer joins. Inner joins return results for matching rows only, while outer joins return matching rows and rows that appear in only one table. There are three types of outer joins: left outer join (returns all rows from the left table), right outer join (returns all rows from the right table), and full outer join (returns all rows from both tables). The characteristic of inner join is to match rows. The left outer join uses NULL to fill the null values of the right table, the right outer join uses NULL to fill the left table null values, and the full outer join uses NULL to fill the null values of both sides of the table.
- Oracle 627 2024-04-30 07:18:17
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- How to use join on in oracle
- The JOIN ON operator in Oracle is used to join tables based on common columns. Its syntax is: SELECT ... FROM table name 1 JOIN table name 2 ON table name 1.common column = table name 2.common column. This operator can be used to join multiple tables and supports other comparison operators and AND operators.
- Oracle 709 2024-04-30 07:15:23
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- How to use union all in oracle
- UNION ALL is used in Oracle to merge result sets from different tables or subqueries while retaining duplicate rows. The specific usage is as follows: merge rows in different tables: SELECT FROM table 1 UNION ALL SELECT FROM table 2 merge duplicate rows in the same table: SELECT FROM table UNION ALL SELECT FROM table
- Oracle 545 2024-04-30 07:09:13
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- How to use union in oracle
- The usage of UNION in Oracle is to merge multiple query result sets with the same structure into a single result set. This operator removes duplicate records unless UNION ALL is used, which merges all records, including duplicates.
- Oracle 781 2024-04-30 07:06:15
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- length usage in oracle
- The LENGTH function returns the number of characters in a string. It accepts CHAR, VARCHAR2, NCHAR, and NVARCHAR2 data types as input, ignores whitespace, and returns an integer result.
- Oracle 1143 2024-04-30 07:00:28
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- casewhen usage in oracle
- The CASE WHEN statement in Oracle is used to return different values based on conditions. Syntax: CASE WHEN condition THEN result ELSE default_result END. Usage: 1. Condition check: WHEN clause contains the condition and returned result; 2. Default result: ELSE clause specifies the default result when any condition is not met. Example: Return income_level based on salary value: salary > 5000: high income; 3000 ≤ salary ≤ 5000: middle income; salary < 3000: low income.
- Oracle 390 2024-04-30 06:57:14
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- How to use sum function in oracle
- The SUM function calculates the sum of a series of values in Oracle. Syntax: SUM(expression), where expression is a numeric expression or column name. It can sum all row values in a column, or sum rows that meet a specific condition via a WHERE clause. The SUM function returns a value of type NUMBER and returns a positive number even if the argument is negative. It supports advanced usage, such as with GROUP BY and HAVING clauses, and as a window function.
- Oracle 658 2024-04-30 06:54:16
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- How to use having in oracle
- The HAVING clause is used to filter the result set grouped by the GROUP BY clause. Its syntax is HAVING <condition>, where <condition> is a Boolean expression. The difference with the WHERE clause is that the HAVING clause filters groups after aggregation, while the WHERE clause filters rows before aggregation. It can be used to filter grouped result sets, perform aggregate calculations on data, create hierarchical reports, or summarize queries.
- Oracle 599 2024-04-30 06:51:16
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