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- What symbols are used to connect strings to the database in Oracle?
- Oracle uses the "||" symbol to concatenate strings. The usage method is as follows: connect the strings to be connected with the "||" symbol; the priority of string connection is low, and parentheses need to be used to ensure the priority; an empty string will still be an empty string after connection; NULL value connection is still NULL.
- Oracle 942 2024-05-08 19:36:17
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- How to use with in oracle
- The WITH clause creates temporary tables or views in Oracle. It is used to create complex temporary tables or views, rename query results and improve query performance: Create temporary tables: WITH clause_name AS (subquery) Rename query results: WITH clause_name AS ( subquery) to improve query performance: storing subqueries in temporary tables improves performance
- Oracle 716 2024-05-08 19:33:16
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- What type is rowid in oracle?
- A ROWID is a proprietary data type in Oracle that uniquely identifies a row in a physical database because it is unique and persistent and persists when the row is moved or updated. Advantages include fast retrieval, can be obtained using the ROWID pseudo-column, and can be used to quickly find, compare, and move rows.
- Oracle 1011 2024-05-08 19:27:17
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- How to replace string in oracle
- The method of replacing strings in Oracle is to use the REPLACE function. The syntax of this function is: REPLACE(string, search_string, replace_string). Usage steps: 1. Identify the substring to be replaced; 2. Determine the new string to replace the substring; 3. Use the REPLACE function to replace. Advanced usage includes: multiple replacements, case sensitivity, special character replacement, etc.
- Oracle 475 2024-05-08 19:24:20
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- How to convert string to number in oracle
- Oracle provides multiple methods to convert strings to numbers: TO_NUMBER function: Converts strings to numeric types using the specified format model. NUMTOSTR function: Converts a string to a numeric type and back to a string. VAL function: directly converts a string to a numeric type without checking the format.
- Oracle 475 2024-05-08 19:21:18
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- Tonumber usage in oracle
- The TO_NUMBER function in Oracle converts a string into a numeric value. It takes a string argument, with the optional format_mask specifying the number format in the string. It returns a value of type NUMBER, or NULL if the conversion fails.
- Oracle 536 2024-05-08 19:18:17
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- What is used to express a certain character contained in Oracle?
- The representation method of containing a certain character in Oracle is: using the wildcard character %, which means matching any number of any characters. Usage: SELECT * FROM table_name WHERE column_name LIKE '%character%'. In addition, Oracle also provides other wildcards: _ matches a single character; [] matches a single character within square brackets; [^] matches a single character outside square brackets.
- Oracle 372 2024-05-08 19:15:31
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- What function is used to define a certain character in Oracle?
- INSTR function is used in Oracle to check if a string contains a specific character. Syntax: INSTR(string, substring, [start_position], [occurrence]). It returns the index position of the first occurrence of the substring in the string, or 0 if no match is found.
- Oracle 374 2024-05-08 19:12:17
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- What function is used to represent a certain character in Oracle?
- In Oracle, you can use the INSTR function to determine whether a string contains a certain character. For example, to find the presence of the character "r" in the string "Oracle", you would use INSTR('Oracle', 'r'). The function returns the index position of the first occurrence of the character if found, or 0 if not found.
- Oracle 1041 2024-05-08 19:06:20
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- What is the difference between stored procedures and functions in oracle
- The main difference between stored procedures and functions in Oracle: stored procedures have no explicit return type, while functions return an explicit type value. Stored procedures must handle exceptions explicitly, whereas exceptions in functions can be propagated to the caller. Stored procedures are typically executed as part of a transaction, whereas functions are not transactional. A stored procedure must contain a PL/SQL block, while a function can contain a PL/SQL block or just an expression.
- Oracle 745 2024-05-08 19:03:19
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- How to determine whether two strings are contained in oracle
- In Oracle, you can use the nested INSTR function to determine whether a string contains two substrings at the same time: when INSTR(string1, string2a) is greater than 0 and INSTR(string1, string2b) is greater than 0, it is included; otherwise, it is not included.
- Oracle 745 2024-05-08 19:00:25
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- What does (+) mean in oracle
- The (+) symbol in Oracle represents the outer join symbol, which is used to join tables and return a result set containing all participating table rows, allowing you to retrieve records in the foreign key table even if no matching record exists in the primary key table. There are three types of outer joins: left outer join, right outer join and full outer join.
- Oracle 903 2024-05-08 18:57:16
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- The difference between not equal to null and is not null in oracle
- NOT NULL is a column constraint that prohibits the insertion of NULL values; IS NOT NULL is a check operator that evaluates whether the column does not contain NULL values.
- Oracle 1093 2024-05-08 18:54:17
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- Why does Oracle filter out null if it is not equal to 1?
- In Oracle, not equal to 1 queries filter out Null values because: Null values are not equal to any value, including 1. Oracle uses three-valued logic to handle Null values, namely true, false, and unknown. A comparison of Null to non-Null values always returns Unknown unless the comparison is Null to Null (which returns True). Queries that are not equal to 1 treat Null values as unknown and filter them out based on Oracle's Null handling mechanism.
- Oracle 1072 2024-05-08 18:51:16
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- How to write not equal to a certain value in Oracle
- The syntax in Oracle to indicate that it is not equal to a certain value is "column_name <> value". For example, if you want to query employees whose salary is not equal to $1,000, you can use the "SELECT emp_id, salary FROM employees WHERE salary <> 1000;" query.
- Oracle 378 2024-05-08 18:48:15
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