Collation derivation and determination rules for sql operations database theory _ data recovery

The process of determining the collation of a character result of an SQL operation is called collation derivation. Database of state incentives for renewables and efficiency 911 database Such operation may be an operator, column reference, character literal, bind variable reference, function call, CASE expression, or a query clause.

The derived collation and coercibility level of an operation’s result is based on the collations and coercibility levels of the operation’s arguments.


Data recovery usb stick Icd 9 database A derivation-relevant character argument of an operation is an argument used to derive the collation of the operator’s result. Database companies Cloud 9 database An operator may have zero or more derivation-relevant character arguments, and zero or more other character arguments, such as flags or other control information not directly interacting with the derivation-relevant arguments. Database application Database 10g An argument is considered derivation-relevant, if its value is included in the result, either after some transformation or without undergoing any transformation.

An argument that is a format model, a pattern, a flag string, or a key into a virtual table of system information is not considered a derivation-relevant argument.

Data recovery miami For example, the built-in function TO_CHAR(arg1,arg2,arg3) has no derivation-relevant arguments, as the main argument arg1 is not of a character data type. Database online Data recovery fort lauderdale The two character arguments arg2 and arg3 are not derivation-relevant arguments as they only define the format and parameters for the conversion of the main argument arg1.

The derived collation and coercibility level of the result of an operation without derivation-relevant arguments are the same as when a character literal would have been put in that expression in the place of the operation.

The following are the collation derivation rules for operations that return character values and have derivation-relevant arguments. Database high availability Data recovery mac These rules are applied recursively in an expression tree. Database utility Data recovery tools These rules are based on the SQL standard version ISO/IEC 9075-2:1999.

If at least one argument has the coercibility level 0, then all the arguments with coercibility level 0 must have the same collation, which is the derived collation of the result. Data recovery zagreb Data recovery pro The coercibility level of the result is 0. Database javascript Data recovery hardware If two arguments with coercibility level 0 have different collations, then an error is reported.

Otherwise, if at least one argument has the coercibility level 1, then the expression result has the coercibility level 1 and no collation is assigned to it.

If all the arguments with LCL have the same collation, then this collation is the derived collation of the result, and the coercibility level of the result is LCL.

Starting from Oracle Database 12.2, collation to be applied by an operation is determined by the derived data-bound collations of its arguments. Database administrator jobs Data recovery free Once a pseudo-collation is determined as the collation to use, NLS_SORT and NLS_COMP session parameters are checked to provide the actual named collation to apply.

The collation determination does not have to apply to the same operation to which collation derivation applies. Data recovery for iphone Data recovery software reviews For example, TO_CHAR function is not collation-sensitive, so it does not need collation determination. Data recovery victoria bc Data recovery wizard But, TO_CHAR function returns a character result that needs a collation declaration, hence collation derivation applies to it. 10k database Data recovery geek squad Conversely, INSTR function needs to match characters and needs a collation determined for this match operation. Data recovery software mac Data recovery software However, the result of INSTR function is a number, hence no collation derivation is required for it.

The determination-relevant character argument of an operation is an argument used to determine the collation to be used by the operation. Cost of data recovery from hard drive Data recovery android A collation-sensitive operation may have one or more determination-relevant character arguments and zero or more other character arguments, such as flags or other control information not directly interacting with the determination-relevant arguments.

An argument is considered determination-relevant, if its value is compared during the evaluation of an operation. S cerevisiae database Data recovery app An argument that is a format model, a flag string, or a key into a virtual table of system information is not considered a determination-relevant argument. Snl database Data recovery after factory reset However, a pattern argument can be a determination-relevant argument. Database 4500 Data recovery agent For example, two of the three arguments of the LIKE predicate – argument and pattern – are determination-relevant arguments. Data recovery miami fl Data recovery android app The third argument – the escape character – is not considered determination-relevant argument. Data recovery sd card Data recovery after format Another example is the built-in function REGEXP_COUNT, which has four arguments – source_char, pattern, position, and match_param. Uottawa database Data recovery apple The determination-relevant arguments are source_char and pattern, which contain the strings to be compared. Top 10 data recovery software free download Data recovery austin The non-determination-relevant character argument are position, which is numeric, and match_param, which provides parameters for the matching operation.

The following are the collation determination rules to determine the collation to use for an operation with determination-relevant character arguments arg1, arg2, …, argn. Database query optimization Data recovery advisor These rules are based on the SQL standard version ISO/IEC 9075-2:1999.

If operation is the equality condition and is used to enforce a foreign key constraint, then the collation to be used is the declared collation of the primary or unique key column being referenced. Qmobile data recovery Data recovery android free This declared collation must be the same as the declared collation of the foreign key column.

Otherwise, if at least one argument has the derived coercibility level 0, then all the arguments with coercibility level 0 must have the same collation, and this collation is used by the operation. No 1 data recovery software A data recovery tool If two arguments with coercibility level 0 have different collations, then an error is reported.

When the determined collation is a pseudo-collation, then the affected operation must refer to the session or database settings NLS_SORT or NLS_COMP or both to determine the actual named collation to apply. Data recovery iphone free Data recovery best buy The database settings are used for expressions in virtual columns, CHECK constraints, and fine grained auditing (FGA) rules.

The collation determination rules for an operation involving a CLOB or an NCLOB data type value must result in the pseudo-collation USING_NLS_COMP, otherwise an error is reported.

Some conditions, set operators, and query clauses have arguments which are expression lists. Database 11g Data recovery boston In this case, collation determination is performed on the corresponding compared elements of each of the arguments in the expression list. Data recovery thumb drive Data recovery boot disk For example, in the condition:

the collation is determined separately for the pairs of compared elements. Data recovery hardware tools Data recovery business First, the collation determination rules are applied to expr1 and expr3. Os x data recovery Data recovery broken hard drive Then, the rules are applied to expr2 and expr4. R studio data recovery download Data recovery bad hard drive When the condition is evaluated, values of expr1 are compared to values of expr3 using the first determined collation and values of expr2 are compared to values of expr4 using the second determined collation. Data recovery western digital Data recovery best Similarly, in the query:

the collation determination rules are first applied to expr1 and expr3, then to expr2 and expr4. Top 5 data recovery software Data recovery boston ma When the MINUS operator is evaluated, values of expr1 are compared to values of expr3 using the first determined collation and values of expr2 are compared to values of expr4 using the second determined collation.

rows are sorted first on values of expr1 using the derived collation expr1, then ties are broken by sorting on values of expr2 using the derived collation expr2, and then on values of expr3 using the derived collation expr3. Data recovery mac Bplan data recovery Each position in the ORDER BY list is treated like a separate comparison operator for row values.

Collation for each column of the resulting row set is derived separately by combining collations of columns from each of the two argument row sets.

Special case: if an argument a i2 (1<=i<=m) belongs to a recursive member in a WITH clause and it is calculated recursively, then the collation is derived from the corresponding argument a i1 of the anchor member.

Collation for each column of the resulting row set is derived separately by combining collations of columns from each of the two argument row sets.

Collation for comparison of each column of the argument row set is determined separately by combining collations of columns from each of the two argument row sets.

Collation for each column of the resulting row set is derived separately by combining collations of columns from each of the two argument row sets.

Collation for comparison of each column of the argument row set is determined separately by combining collations of columns from each of the two argument row sets.

Collation for each column of the resulting row set is derived separately by combining collations of columns from each of the two argument row sets.

Collation for comparison of each column of the argument row set is determined separately by combining collations of columns from each of the two argument row sets.

When two lists are compared, the collation determination is performed separately and independently for each of the two character data type elements at the same index in both the lists.

If the cell reference a 1 exists before execution of the enclosing model clause and is not null when the function is evaluated, then a 2 else a 3

Minimal position in a 1 at which regular expression a 2 matches substring of string a 1 for the a 4-th time according to flags a 6 starting matching at position a 3; a 5 and a 7 control which position is actually returned

Replace with string a 3 all matches or the a 5-th match of regular expression a 2 with a substring of string a 1 according to flags a 6 starting matching at position a 4

Return the a 4-th matching substring of regular expression a 2 in string a 1 according to flags a 5 starting matching at position a 3. Database website Data recovery cost if a 6 is specified, it is the index of sub-expression to return in place of the whole matching substring.

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